[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fUVs0h-A_6aYD-mIu3euzloVtWFEGLfzU9tJ4s6Ro3O8":36,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":133,"$fucxFBm2ZjZfGSdmdRaSNGBI_F0jJme4f0GTvzUhQfL8":198},[4,8,12,16,20,24,28,32],{"title":5,"slug":6,"path":7},"About Microbeonline.com","about-microbeonline-com","\u002Fabout-microbeonline-com\u002F",{"title":9,"slug":10,"path":11},"About Me","about-me","\u002Fabout-microbeonline-com\u002Fabout-me\u002F",{"title":13,"slug":14,"path":15},"Advertise with Us","advertise-us","\u002Fadvertise-us\u002F",{"title":17,"slug":18,"path":19},"Privacy Policy","privacy-policy","\u002Fprivacy-policy\u002F",{"title":21,"slug":22,"path":23},"Abbreviations","abbreviations","\u002Fabbreviations\u002F",{"title":25,"slug":26,"path":27},"Microbes","microbes","\u002Fmicrobes\u002F",{"title":29,"slug":30,"path":31},"Books","recommended-books","\u002Frecommended-books\u002F",{"title":33,"slug":34,"path":35},"Utilization Tests for Bacterial Identification","utilization-tests","\u002Futilization-tests\u002F",{"type":37,"data":38},"blog",{"slug":39,"title":40,"description":41,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":44,"lastUpdatedDate":45,"draft":46,"category":47,"image":42,"body":48,"faq":49,"commentsClosed":46,"tags":68,"related":71,"comments":129},"natural-killer-cells","Natural Killer (NK) Cells: Missing-Self Recognition and Function","\u003Cp>What natural killer (NK) cells are, how the missing-self mechanism lets them catch virus-infected and tumor cells that hide from T cells, and how they bridge innate and adaptive immunity. For micro and health-science students.\u003C\u002Fp>",null,"Acharya Tankeshwar","2026-08-08","2026-08-09",false,"immunology","A virus faces a problem. To survive, an infected cell displays viral fragments on its MHC class I molecules, which flags it for killing by cytotoxic T cells. So some clever viruses, and many tumors, evolved a trick: they stop displaying MHC class I altogether. No display, no flag, and the cytotoxic T cell walks past. It should be the perfect escape.\n\nBut it is not, because the body has a second guard that works on the opposite rule. This guard does not look for a danger signal. **It looks for the reassuring \"I am healthy\" signal that every normal cell shows**, **and it kills any cell that has stopped showing it.** By hiding from the T cell, the infected cell exposes itself to this second killer. That killer is the natural killer cell, and this elegant trap is the heart of what makes NK cells fascinating.\n\n## What is a natural killer cell?\n\nA natural killer (NK) cell is a type of lymphocyte that kills virus-infected cells and tumor cells without needing prior exposure or training. The name says it plainly: it is \"naturally\" ready to kill, from the start.\n\nNK cells are an unusual case in the immune system. By lineage, they are lymphocytes, made from the same lymphoid progenitor that gives rise to T and B cells. But by behavior, they act like innate immune cells: they need no education, they recognize no single specific antigen, and they keep little immunological memory. So an NK cell is a lymphocyte that behaves like an innate cell, which places it at the border between the two systems.\n\nUnlike T and B cells, NK cells do not rearrange their receptor genes and do not have one unique specificity each. Instead, every NK cell carries the same general set of sensing receptors, and it makes its kill-or-spare decision on the spot.\n\n## The key idea: missing-self recognition\n\nThe central concept of NK biology is how they decide what to kill. A cytotoxic T cell asks, \"do I see a specific foreign fragment?\" An NK cell asks the opposite question: \"is the healthy self signal missing?\"\n\nThat healthy self signal is MHC class I. Almost every normal cell in the body displays MHC class I on its surface. NK cells carry inhibitory receptors that recognize MHC class I, and as long as those receptors detect enough MHC class I, they send a \"do not kill\" signal. A healthy cell, showing normal MHC class I, is therefore left alone.\n\n\u003Cfigure>\n\u003Cimg src=\"https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002Fnatural-killer-cells.jpg\" alt=\"Natural Killer Cells\" width=\"362\" height=\"341\" draggable=\"false\" contenteditable=\"false\">\u003Cfigcaption>Figure: Natural Killer Cells\u003C\u002Ffigcaption>\n\u003C\u002Ffigure>\n\nBut when a cell loses or reduces its MHC class I, the inhibitory signal disappears. The NK cell no longer receives \"do not kill,\" and it attacks. This is called missing-self recognition: the NK cell kills the cell that has stopped proving it is healthy.\n\nThis is exactly why the viral escape trick backfires. A virus that downregulates MHC class I to hide from cytotoxic T cells removes the very signal that was protecting the cell from NK cells. The two guards cover each other's blind spots: T cells catch cells that display something foreign, and NK cells catch cells that have stopped displaying self.\n\n## The balance of signals\n\nMissing-self is the core idea, but the full picture is a balance. NK cells carry two kinds of receptors, and the outcome depends on which signal wins.\n\nInhibitory receptors recognize MHC class I on healthy cells and say \"do not kill.\" In humans these include the killer-cell immunoglobulin-like receptors (KIRs).\n\nActivating receptors recognize stress signals, molecules that infected, damaged, or transformed cells display when they are in trouble. These say \"kill.\"\n\nEvery cell the NK cell touches is weighed on this balance. A healthy cell shows strong MHC class I (strong \"do not kill\") and few stress signals, so it is spared. An infected or tumor cell often shows reduced MHC class I (weak \"do not kill\") and raised stress signals (strong \"kill\"), so it is destroyed. The NK cell fires only when activating signals outweigh inhibitory ones.\n\nThis two-signal balance is more complete than missing-self alone: a cell can become an NK target either by losing MHC class I or by raising stress signals, and often by doing both at once.\n\n## How NK cells kill\n\nOnce an NK cell decides to kill, it uses the same tools as a cytotoxic T cell. It releases perforin, which forms pores in the target cell membrane, and granzymes, which enter and trigger apoptosis. The target cell is driven to kill itself cleanly, containing the threat.\n\nNK cells also release cytokines, especially interferon-gamma, which activates macrophages and shapes the wider immune response. So NK cells both kill directly and signal to the rest of the immune system.\n\n## The adaptive side: antibody-dependent killing (ADCC)\n\nNK cells are mostly innate, but they have one important link to the adaptive immune system. NK cells carry a receptor called CD16 that recognizes the tail (Fc portion) of antibodies. When antibodies coat a target cell, the NK cell's CD16 grabs those antibody tails, and this triggers the NK cell to kill the coated cell. This is antibody-dependent cellular cytotoxicity (ADCC).\n\nADCC is where innate and adaptive immunity meet in the NK cell: the antibody (made by the adaptive system) directs the NK cell (an innate killer) to a specific target. This is also covered from the antibody side in the article on the functions of antibodies.\n\n## NK cells in innate and adaptive immunity\n\nPulling it together, the NK cell sits in both systems:\n\nOn the innate side, it responds immediately, without training, using the missing-self and stress-signal logic. It is one of the first responders to viral infection and to newly arising tumor cells, long before T cells are ready.\n\nOn the adaptive side, through ADCC it acts on the instructions of antibodies, and through its interferon-gamma it shapes the adaptive response that follows.\n\nThis dual role is why NK cells are often described as a bridge between innate and adaptive immunity.\n\n## NK cell vs cytotoxic T cell\n\nThese two killers are easy to confuse because both use perforin and granzymes to kill infected and tumor cells. The difference is in how they choose their target.\n\n| Feature | NK cell | Cytotoxic (CD8) T cell |\n| --- | --- | --- |\n| Lineage | Lymphocyte | Lymphocyte |\n| System | Mainly innate | Adaptive |\n| Needs prior exposure | No | Yes (must be activated) |\n| Recognizes | Missing or reduced MHC class I, plus stress signals | Specific antigen on MHC class I |\n| Kills a cell that LOST MHC class I | Yes | No (it needs MHC class I to see antigen) |\n| Killing mechanism | Perforin, granzyme, ADCC | Perforin, granzyme, Fas-FasL |\n| Memory | Little | Yes |\n\nThe most important row is the middle one: a cell that loses MHC class I becomes invisible to a cytotoxic T cell but a target for an NK cell. They are perfect complements.\n\n## How to remember\n\n**NK asks \"where is the self signal?\"** A T cell looks for a foreign flag; an NK cell looks for the missing healthy flag (MHC class I). No self signal, no protection.\n\n**The viral trap: hiding from T cells exposes you to NK cells.** Downregulating MHC class I escapes cytotoxic T cells but triggers NK cells. You cannot hide from both by the same trick.\n\n**Balance of two signals: inhibitory (MHC I, \"do not kill\") vs activating (stress, \"kill\").** The NK cell fires when \"kill\" outweighs \"do not kill.\"\n\n**Same weapons as CTLs, opposite logic.** NK cells and cytotoxic T cells both use perforin and granzyme, but the T cell needs to SEE antigen on MHC I, while the NK cell kills when MHC I is GONE.\n\n**CD16 is the adaptive handshake.** CD16 binds antibody tails and lets NK cells kill antibody-coated cells (ADCC), linking them to the adaptive system.\n\n## Key exam facts in one table\n\n| Fact | Detail |\n| --- | --- |\n| Lineage | Lymphocyte (lymphoid progenitor) |\n| System | Mainly innate; bridges to adaptive |\n| Needs training | No |\n| Core recognition | Missing-self (loss of MHC class I) |\n| Inhibitory receptors | KIRs; recognize MHC class I (\"do not kill\") |\n| Activating receptors | Recognize stress signals (\"kill\") |\n| Decision | Fires when activating outweighs inhibitory |\n| Killing mechanism | Perforin + granzyme → apoptosis |\n| Key cytokine released | Interferon-gamma |\n| ADCC receptor | CD16 (binds antibody Fc) |\n| Kills MHC-I-negative cells | Yes (unlike CD8 T cells) |\n| Main targets | Virus-infected cells, tumor cells |\n\n## Where students get confused\n\n**\"NK cells are a type of T cell.\"** No. NK cells are lymphocytes, but not T cells and not B cells. They do not rearrange receptor genes, do not have one specific antigen, and are not MHC-restricted. They are lymphocytes that behave like innate cells.\n\n**\"NK cells kill cells that show MHC class I.\"** The opposite. MHC class I is the \"do not kill\" signal. NK cells kill cells that have LOST or reduced MHC class I. A normal cell with full MHC class I is protected.\n\n**\"NK cells need to be activated by a specific antigen like T cells.\"** No. NK cells need no prior exposure and recognize no single specific antigen. They read the balance of inhibitory and activating signals on the spot.\n\n**\"NK cells are purely innate.\"** Mostly, but not purely. Through ADCC (CD16 binding antibody), they act on adaptive instructions, and their cytokines shape adaptive responses. They straddle both systems.\n\n**\"NK cells and cytotoxic T cells do the same job the same way.\"** They share the perforin-granzyme weapon, but choose targets by opposite rules. The T cell needs MHC class I present to see antigen; the NK cell attacks when MHC class I is absent. This is why they complement each other so well.\n\n### References\n\n1. Abbas AK, Lichtman AH, Pillai S. *Cellular and Molecular Immunology*. 10th ed. Elsevier; 2022.\n2. Punt J, Stranford SA, Jones PP, Owen JA. *Kuby Immunology*. 8th ed. W.H. Freeman; 2019.\n3. Vivier E, Tomasello E, Baratin M, Walzer T, Ugolini S. Functions of natural killer cells. *Nat Immunol*. 2008;9(5):503–510. \u003Chttps:\u002F\u002Fdoi.org\u002F10.1038\u002Fni1582>",[50,53,56,59,62,65],{"question":51,"answer":52},"\u003Cp>What is a natural killer cell?\u003C\u002Fp>","\u003Cp>A natural killer (NK) cell is a lymphocyte that kills virus-infected and tumor cells without prior exposure or training. It is mainly part of the innate immune system, though it also links to the adaptive system.\u003C\u002Fp>",{"question":54,"answer":55},"\u003Cp>What is missing-self recognition?\u003C\u002Fp>","\u003Cp>It is how NK cells decide what to kill. Healthy cells display MHC class I, which NK cells read as a \"do not kill\" signal. When a cell loses MHC class I, that signal disappears and the NK cell attacks. NK cells kill the cell that has stopped showing the healthy self signal.\u003C\u002Fp>",{"question":57,"answer":58},"\u003Cp>Why can NK cells kill cells that cytotoxic T cells cannot?\u003C\u002Fp>","\u003Cp>Some viruses and tumors hide from cytotoxic T cells by removing MHC class I, since T cells need MHC class I to see antigen. But removing MHC class I is exactly what triggers NK cells. So NK cells catch the cells that escape T cells.\u003C\u002Fp>",{"question":60,"answer":61},"\u003Cp>How do NK cells kill their targets?\u003C\u002Fp>","\u003Cp>Mainly with perforin and granzymes, the same tools cytotoxic T cells use. Perforin makes pores in the target, granzymes enter and trigger apoptosis. NK cells also kill antibody-coated cells through ADCC and release interferon-gamma.\u003C\u002Fp>",{"question":63,"answer":64},"\u003Cp>Are NK cells part of innate or adaptive immunity?\u003C\u002Fp>","\u003Cp>Mainly innate, because they act immediately without training. But they also bridge to the adaptive system through ADCC, where antibodies direct their killing, and through the cytokines they release.\u003C\u002Fp>",{"question":66,"answer":67},"\u003Cp>What is the difference between an NK cell and a cytotoxic T cell?\u003C\u002Fp>","\u003Cp>Both use perforin and granzyme to kill infected and tumor cells, but they choose targets oppositely. A cytotoxic T cell needs to see a specific antigen on MHC class I. An NK cell attacks when MHC class I is missing. They complement each other.\u003C\u002Fp>",[69,70],"adaptive-immunity","innate-immunity",[72,98,104],{"slug":73,"title":74,"description":75,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":76,"lastUpdatedDate":45,"draft":46,"category":77,"image":42,"faq":78,"tags":97},"difference-between-b-cells-t-cells","Difference Between B Cells and T Cells: Why One Sees Antigen Directly and the Other Cannot","\u003Cp>B cells vs T cells compared point by point: where they mature, how each recognizes antigen, their receptors, CD markers, and blood proportions. The one difference that explains all the others, plus the exam points students most often confuse.\u003C\u002Fp>","2019-04-08","difference-between",[79,82,85,88,91,94],{"question":80,"answer":81},"\u003Cp>What is the main difference between B cells and T cells?\u003C\u002Fp>","\u003Cp>The core difference is how they recognize antigen. A B cell binds free, unprocessed antigen directly, using its membrane-bound antibody. A T cell cannot bind free antigen at all; it only recognizes antigen after it has been processed into a peptide and displayed on an MHC molecule on another cell. Nearly every other difference follows from this one.\u003C\u002Fp>",{"question":83,"answer":84},"\u003Cp>Where do B cells and T cells mature?\u003C\u002Fp>","\u003Cp>Both are made in the bone marrow, but they mature in different places. B cells mature in the bone marrow itself. T cells leave the bone marrow and travel to the thymus to mature, which is where the T in T cell comes from.\u003C\u002Fp>",{"question":86,"answer":87},"\u003Cp>What do B cells and T cells do?\u003C\u002Fp>","\u003Cp>B cells drive humoral immunity: their plasma cell offspring produce antibodies. T cells drive cell-mediated immunity: cytotoxic (CD8) T cells kill infected or cancerous cells directly, while helper (CD4) T cells coordinate the immune response, including helping B cells make antibody.\u003C\u002Fp>",{"question":89,"answer":90},"\u003Cp>Why do T cells need MHC but B cells do not?\u003C\u002Fp>","\u003Cp>A B cell receptor is essentially an antibody, which can grip a whole antigen on its own. A T cell receptor is built differently and can only engage a short peptide held out on an MHC molecule. So T cells depend on other cells to process and present antigen, while B cells can recognize it directly.\u003C\u002Fp>",{"question":92,"answer":93},"\u003Cp>What is the difference between CD4 and CD8 T cells?\u003C\u002Fp>","\u003Cp>CD4 marks helper T cells, which coordinate the immune response and pair with MHC class II. CD8 marks cytotoxic (killer) T cells, which destroy infected cells and pair with MHC class I. A simple memory aid is 4 times 2 equals 8: CD4 with class II, CD8 with class I.\u003C\u002Fp>",{"question":95,"answer":96},"\u003Cp>Which are more numerous in the blood, B cells or T cells?\u003C\u002Fp>","\u003Cp>T cells are far more numerous, making up about 70 to 80 percent of the lymphocytes in peripheral blood. B cells make up only about 10 to 15 percent. The remainder includes natural killer cells.\u003C\u002Fp>",[69],{"slug":99,"title":100,"description":101,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":44,"lastUpdatedDate":44,"draft":46,"category":47,"image":42,"faq":102,"tags":103},"antigen-presenting-cells","Antigen-Presenting Cells: Professional and Non-Professional APCs","\u003Cp>What antigen-presenting cells are, the three professional APCs (dendritic cells, macrophages, B cells), how they differ from non-professional APCs, and what makes a cell \"professional.\" For micro and health-science students.\u003C\u002Fp>",[],[69],{"slug":105,"title":106,"description":107,"seoTitle":42,"seoDescription":42,"author":43,"createdDate":108,"lastUpdatedDate":108,"draft":46,"category":47,"image":42,"faq":109,"tags":128},"immune-tolerance","Immune Tolerance: How We Recognize Self from Non-Self","\u003Cp>How the immune system learns self-tolerance: central and peripheral tolerance, clonal deletion, receptor editing, anergy, Tregs, and autoimmunity.\u003C\u002Fp>","2026-08-19",[110,113,116,119,122,125],{"question":111,"answer":112},"\u003Cp>What is immune tolerance in simple terms?\u003C\u002Fp>","\u003Cp>It is the immune system's ability to not attack a specific target. Self-tolerance is the version that stops it from attacking the body's own tissues while still letting it fight infections.\u003C\u002Fp>",{"question":114,"answer":115},"\u003Cp>What is the difference between central and peripheral tolerance?\u003C\u002Fp>","\u003Cp>Central tolerance removes or reprograms self-reactive lymphocytes while they are still developing in the thymus and bone marrow. Peripheral tolerance controls the self-reactive cells that escape, out in the body, using anergy, regulatory T cells, and checkpoints.\u003C\u002Fp>",{"question":117,"answer":118},"\u003Cp>What is clonal deletion?\u003C\u002Fp>","\u003Cp>It is the removal, by programmed cell death, of a lymphocyte clone that reacts too strongly to a self-antigen. It happens both in the thymus (T cells) and the bone marrow (B cells).\u003C\u002Fp>",{"question":120,"answer":121},"\u003Cp>What is receptor editing?\u003C\u002Fp>","\u003Cp>It is a rescue mechanism in immature B cells: instead of dying, a self-reactive B cell rebuilds its receptor to a new specificity that no longer binds self.\u003C\u002Fp>",{"question":123,"answer":124},"\u003Cp>What is the difference between clonal deletion and anergy?\u003C\u002Fp>","\u003Cp>Clonal deletion kills the self-reactive cell. Anergy keeps it alive but locks it in an unresponsive state, so it can no longer act.\u003C\u002Fp>",{"question":126,"answer":127},"\u003Cp>How does tolerance failure cause autoimmune disease?\u003C\u002Fp>","\u003Cp>When the mechanisms that delete, silence, or suppress self-reactive cells fail, or when a hidden self-antigen is suddenly exposed, those cells attack healthy tissue. The organ they target determines the disease, for example beta cells in type 1 diabetes or thyroid in Hashimoto thyroiditis.\u003C\u002Fp>",[69],{"enabled":130,"threads":131,"total":132},true,[],0,[134,140,147,154,160,165,171,176,182,185,192],{"slug":135,"name":43,"description":136,"image":137,"body":138,"postCount":139},"acharya-tankeshwar","Editor-in-chief","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Ftankeshwar-acharya-author-microbeonline.jpg","***Tankeshwar Acharya, MSc (Medical Microbiology)***\n\n*Tankeshwar Acharya is an Assistant Professor in the Department of Microbiology at Patan Academy of Health Sciences (PAHS), Nepal, where he has been teaching and practicing clinical microbiology for over 14 years. He is the founder of Microbe Online, one of the leading free microbiology education resources on the web, covering bacteriology, mycology, parasitology, immunology, and clinical laboratory diagnostics written from direct experience in both the classroom and the diagnostic laboratory.*",468,{"slug":141,"name":142,"description":143,"image":144,"body":145,"postCount":146},"ashma-shrestha","Ashma Shrestha","SEO Copywriter and Science Communicator\nKathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fashma-shrestha.png","Ashma Shrestha holds a Master of Science in Medical Microbiology from the Institute of Science and Technology (IOST), Tribhuvan University, Nepal, where she developed a strong foundation in virology, molecular biology, and diagnostic microbiology.\n\nShe now works as an SEO Copywriter at Resolution Digital, where she combines her scientific training with research-driven content strategy. She is certified in Google Analytics and Google Business Profile (GBP), and brings a data-informed approach to science communication writing content that is not only accurate but structured to reach and serve the students who need it most.\n\nAt microbeonline, Ashma contributes articles primarily in virology and molecular biology, areas she finds most compelling for their mechanistic depth and their growing clinical relevance. Her writing reflects the same standard the site is built on: factual rigor, clear explanation of the *why* behind microbiology concepts, and content that helps students move from memorization to genuine understanding.\n\nShe is passionate about making complex microbiological concepts accessible without sacrificing accuracy; a skill that sits at the intersection of her scientific training and her professional work in content and SEO.",78,{"slug":148,"name":149,"description":150,"image":151,"body":152,"postCount":153},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fsushmita-baniya-1.png","Sushmita Baniya holds an M.Sc. in Medical Microbiology from Tribhuvan University (National College), with a research focus in Genetics and Molecular Biology. She is actively involved in teaching and research in the field of microbiology.",26,{"slug":155,"name":156,"description":150,"image":157,"body":158,"postCount":159},"samikshya-acharya","Samikshya Acharya","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fsamikshya-acharya.jpeg","Samikshya Sharma completed her postgraduate studies in Medical Microbiology at the Central Department of Microbiology, Tribhuvan University, Nepal. She contributes to Microbeonline with the goal of making foundational and clinical microbiology concepts clear and useful for students in medical, laboratory science, and allied health programs.",20,{"slug":161,"name":162,"description":150,"image":42,"body":163,"postCount":164},"alisha-tripathi","Alisha Tripathi","Alisha Tripathi holds an M.Sc. in Medical Microbiology from National College, Tribhuvan University. With over a year of teaching experience, her academic interests span Molecular Biology, Immunology, and Genetics.",6,{"slug":166,"name":167,"description":168,"image":42,"body":169,"postCount":170},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor","Aastha Shrestha is a Biotechnology graduate with an M.Sc. from National College, Tribhuvan University. Her academic interests center on Molecular Biology and Immunology; two fields that are increasingly converging in modern diagnostic and clinical microbiology. \n\nShe contributes to Microbeonline with the goal of making complex concepts in these areas approachable and exam-relevant for students across medical, biotechnology, and laboratory science programs.",9,{"slug":172,"name":173,"description":174,"image":42,"body":42,"postCount":175},"guest-author","Guest Author","Guest Author \u002F Contributor",1,{"slug":177,"name":178,"description":150,"image":179,"body":180,"postCount":181},"srijana-khanal","Srijana Khanal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fsrijana-khanal-1.png","Srijana Khanal is a microbiology educator with nearly a decade of teaching experience, including her role as faculty in the Microbiology Department at National College, NIST. \n\nHer time in the classroom has given her a clear sense of where students struggle and what explanations actually work, a perspective that directly shapes how she writes.\n\nHer academic interests span Immunology, Genetics, Basic Sciences, and Research Methodology, and she brings the same rigor to her writing that she brought to teaching. Alongside academic writing, she has a passion for creative writing -- an instinct that shows in her ability to make dense scientific material readable without sacrificing accuracy.\n\nShe contributes to Microbeonline to extend her teaching reach beyond the classroom, helping medical and laboratory science students across the region build a stronger foundation in microbiology.",17,{"slug":183,"name":184,"description":174,"image":42,"body":42,"postCount":175},"dr-poonam-acharya","Dr. Poonam Acharya",{"slug":186,"name":187,"description":188,"image":189,"body":190,"postCount":191},"nisha-rijal","Nisha Rijal","Microbiologist and AMR Specialist Kathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fnisha-rijal-1.png","Nisha Rijal is a microbiologist with nearly 15 years of frontline diagnostic and surveillance experience at the National Public Health Laboratory (NPHL), national reference laboratory under the Department of Health Services, Nepal. She currently works as an AMR Support Officer at the World Health Organization (WHO), Nepal, where her work focuses on strengthening antimicrobial resistance surveillance systems and translating AMR data into actionable public health response.\n\nHer research, published in peer-reviewed journals and cited over 220 times, spans some of the most clinically significant infectious disease challenges in Nepal and South Asia: antimicrobial resistance trends in *Vibrio cholerae* across an 11-year national surveillance dataset, sero-epidemiology of scrub typhus in patients with acute febrile illness, lower respiratory tract infections in HIV-positive patients, and gonococcal resistance surveillance. She was a contributor to Nepal's National Antimicrobial Resistance Containment Action Plan, a foundational policy document for AMR governance in Nepal. You can find list of [Nisha Rijal's article here in Google Scholar.](https:\u002F\u002Fscholar.google.com\u002Fcitations?user=N-Ruq54AAAAJ&hl=en)\n\nThis depth of experience is visible in her writing at Microbeonline. Her 53 published articles cover bacteriology, parasitology, mycology, immunology, and laboratory techniques, and are consistently among the most detailed and clinically grounded content on the site. She brings to every article the same standard that national reference laboratory work demands: methodological precision, awareness of real diagnostic constraints, and an understanding of what results actually mean for patient care in resource-limited settings.\n\nHer areas of particular expertise include antimicrobial susceptibility testing and resistance mechanism detection, quality assurance in clinical microbiology, and laboratory-based infectious disease surveillance.\n\n---\n\n*Nisha Rijal contributes to Microbeonline in a personal capacity. Her views and writing do not represent the positions of the World Health Organization or any other institution.*",54,{"slug":193,"name":194,"description":195,"image":196,"body":197,"postCount":175},"padma-shrestha","Padma Shrestha","Author","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fpadma-shrestha.png","Padma Shrestha is from Kathmandu, Nepal. She has completed Masters degree in Medical microbiology from Tribhuvan University. She has great interest in Microbiology and Molecular Biology.",[199,206,212,217,222,227,231,235,239,244,248,253,257,262,267,271,275,279,284,289,293,297,301,306,310,314,318,322,327,332,336,340,344,348,352,356,360,364,368,372,376,380,384,388,392,395,399,403,408,412,416,420,424,428,432,436,440,444,448,452,456,459,463,467,471,475,479,483,486,490],{"slug":200,"name":201,"description":202,"image":203,"body":204,"postCount":205},"gram-negative-cocci","Gram-Negative Cocci and Coccobacilli","Neisseria, Moraxella, Haemophilus and related gram-negative coccal organisms","https:\u002F\u002Fassets.microbeonline.com\u002Ftags\u002Fgram-negative-cocci.png","# Gram Negative Cocci\n\nNeisseria gonorrhoeae, Neisseria meningitides, Moraxella catarrhalis, and other Neisseria spp. are clinically relevant gram-negative cocci.\n\nN. gonorrhoeae is the leading cause of sexually transmitted disease whereas N. meningitides is a leading cause of fatal bacterial meningitis.",14,{"slug":207,"name":208,"description":209,"image":42,"body":210,"postCount":211},"microscopy","Microscopy","Microscope types, components, and microscopy techniques","These are list of blog posts related to microscopy. ",12,{"slug":213,"name":214,"description":215,"image":42,"body":42,"postCount":216},"gram-positive-cocci","Gram-Positive Cocci","Staphylococcus, Streptococcus, Enterococcus, Micrococcus — organisms, diseases, and identification tests",11,{"slug":218,"name":219,"description":220,"image":42,"body":42,"postCount":221},"gram-negative-rods","Gram-Negative Rods (Other than Enterobacteriaceae)","\u003Cp>Gram negative rods other than members of Enterobacteriaceae family such as  Pseudomonas, Acinetobacter and related organisms\u003C\u002Fp>",5,{"slug":223,"name":224,"description":225,"image":42,"body":42,"postCount":226},"gram-positive-rods","Gram-Positive Rods","Bacillus, Clostridium, Listeria, Corynebacterium, Actinomyces and related organisms",8,{"slug":228,"name":229,"description":230,"image":42,"body":42,"postCount":216},"mycobacteria","Mycobacteria","Mycobacterium tuberculosis, leprosy, atypical mycobacteria, and acid-fast organism diagnosis",{"slug":232,"name":233,"description":234,"image":42,"body":42,"postCount":216},"anaerobic-bacteriology","Anaerobic Bacteriology","Anaerobic organisms, anaerobic culture methods, and anaerobic infection diagnosis",{"slug":236,"name":237,"description":238,"image":42,"body":42,"postCount":211},"enterobacteriaceae","Enterobacteriaceae","Identification, differentiation, and clinical significance of Enterobacteriaceae family members",{"slug":240,"name":241,"description":242,"image":42,"body":42,"postCount":243},"spirochetes","Spirochetes","Treponema, Leptospira, Borrelia and spirochetal infections",7,{"slug":245,"name":246,"description":247,"image":42,"body":42,"postCount":205},"food-microbiology","Food Microbiology","Food-borne pathogens, food safety, spoilage, and preservation",{"slug":249,"name":250,"description":251,"image":42,"body":42,"postCount":252},"antimicrobial-susceptibility-testing","Antimicrobial Susceptibility Testing","Methods for testing antibiotic susceptibility in clinical microbiology",21,{"slug":254,"name":255,"description":256,"image":42,"body":42,"postCount":226},"antimicrobials-moa-amr","Antimicrobials (MOA & AMR)","Mechanisms, detection, and clinical significance of antimicrobial resistance",{"slug":258,"name":259,"description":260,"image":42,"body":42,"postCount":261},"sterilization-disinfection","Sterilization and Disinfection","Methods of sterilization and disinfection in healthcare and laboratory settings",10,{"slug":263,"name":264,"description":265,"image":42,"body":42,"postCount":266},"specimen-collection-transport","Specimen Collection and Transport","Collection, handling, and transport of clinical specimens for microbiological testing",27,{"slug":268,"name":269,"description":270,"image":42,"body":42,"postCount":252},"bacterial-structure-physiology","Bacterial Structure and Physiology","Bacterial cell structure, growth, physiology, and environmental factors affecting growth",{"slug":272,"name":273,"description":42,"image":42,"body":274,"postCount":164},"horizontal-gene-transfer","Horizontal Gene Transfer","Articles related to **Horizontal Gene Transfer**",{"slug":276,"name":277,"description":42,"image":42,"body":278,"postCount":261},"chromatography","Chromatography","Information about chromatographic techniques.",{"slug":280,"name":281,"description":282,"image":42,"body":283,"postCount":243},"electrophoresis","Electrophoresis","Information about Electrophoresis Techniques ","Detailed information  about Electrophoresis Techniques ",{"slug":285,"name":286,"description":287,"image":42,"body":288,"postCount":164},"pcr-techniques","PCR Techniques","Information about various types of Polymerase Chain Reaction Techniques ","More detailed information about various types of Polymerase Chain Reaction Techniques ",{"slug":290,"name":291,"description":292,"image":42,"body":42,"postCount":164},"bacteriophage","Bacteriophage","Description about Bacteriophage.",{"slug":294,"name":295,"description":296,"image":42,"body":42,"postCount":164},"malaria","Malaria","It is the collections of articles regarding malarial disease. ",{"slug":298,"name":299,"description":300,"image":42,"body":42,"postCount":164},"anaerobic-culture-techniques","Anaerobic Culture Techniques","Posts related with Anaerobic Culture Techniques.",{"slug":302,"name":303,"description":304,"image":42,"body":42,"postCount":305},"immunoassays","Immunoassays","You will get information about all the diagnostic tests that rely on the specific binding between an antigen and an antibody to detect or quantify a substance.",19,{"slug":307,"name":308,"description":309,"image":42,"body":42,"postCount":243},"biosafety-levels","Biosafety levels ","Articles related to Biosafety Levels",{"slug":311,"name":312,"description":313,"image":42,"body":42,"postCount":221},"environmental-factors","Environmental Factors ","In this case we are talking about growth requirements of microorganisms with deep dive in environmental factors that affect the growth. ",{"slug":315,"name":316,"description":317,"image":42,"body":42,"postCount":164},"pipette","Pipette","Posts related with Pipette. ",{"slug":319,"name":320,"description":321,"image":42,"body":42,"postCount":226},"bacteriology-mcqs","Bacteriology MCQs","This sections lists MCQs in Bacteriology.",{"slug":323,"name":324,"description":325,"image":42,"body":42,"postCount":326},"parasitology-mcqs","Parasitology MCQs","This section lists MCQs in Parasitology.",2,{"slug":328,"name":329,"description":330,"image":42,"body":42,"postCount":331},"virology-mcqs","Virology MCQs","This is the collections of Multiple Choice Questions in Virology.",4,{"slug":333,"name":334,"description":335,"image":42,"body":42,"postCount":221},"mcqs-in-microbiology","MCQs in Microbiology","This section lists the collections of Multiple Choice Questions in General Microbiology Topics. ",{"slug":337,"name":338,"description":339,"image":42,"body":42,"postCount":226},"immunology-mcqs","Immunology MCQs","In this section; we are posting collections of Multiple Choice Questions about Immunology. ",{"slug":341,"name":342,"description":343,"image":42,"body":42,"postCount":170},"microbial-curiosities","Microbial Curiosities","In this clusters, we are posting interesting and unique information about Microorganisms. ",{"slug":345,"name":346,"description":347,"image":42,"body":42,"postCount":252},"bacterial-culture-media","Bacterial Culture Media","Posts related to Bacterial Culture Media. ",{"slug":349,"name":350,"description":351,"image":42,"body":42,"postCount":164},"fungal-culture-media","Fungal Culture Media","Posts related to Fungal Culture Media.",{"slug":353,"name":354,"description":355,"image":42,"body":42,"postCount":221},"motility-test","Motility Test","This lists the procedure regarding various tests methods for bacterial motility.",{"slug":357,"name":358,"description":359,"image":42,"body":42,"postCount":261},"bacterial-enumeration","Bacterial enumeration","These posts are related to isolation and enumeration of bacteria. ",{"slug":361,"name":362,"description":363,"image":42,"body":42,"postCount":326},"gram-positive-coccobacillus","Gram-positive coccobacillus","List of Gram Positive Coccobacilli",{"slug":365,"name":366,"description":367,"image":42,"body":42,"postCount":331},"dimorphic-fungi","Dimorphic Fungi","This is about various dimorphic fungi. ",{"slug":369,"name":370,"description":371,"image":42,"body":42,"postCount":243},"bacterial-classification","Bacterial Classification","These posts are related with various approaches used for the classification of Bacteria. ",{"slug":373,"name":374,"description":375,"image":42,"body":42,"postCount":221},"immunofluorescence","Immunofluorescence ","Various Tests related to Immunofluorescence ",{"slug":377,"name":378,"description":379,"image":42,"body":42,"postCount":170},"antibody-mediated-immunity","Antibody-mediated Immunity","This clusters links the articles that are sharing insights about Antibody-mediated immunity. ",{"slug":381,"name":382,"description":383,"image":42,"body":42,"postCount":243},"hypersensitivity","Hypersensitivity","Articles related to Hypersensitivity.",{"slug":385,"name":386,"description":42,"image":42,"body":42,"postCount":387},"haemophilus","Haemophilus",3,{"slug":389,"name":390,"description":391,"image":42,"body":42,"postCount":331},"sexually-transmitted-infections-stis","Sexually transmitted infections (STIs)","This is the clusters of infections that are transmitted sexually. ",{"slug":69,"name":393,"description":394,"image":42,"body":42,"postCount":211},"Adaptive Immunity","Blog posts related to B Cell Immunity and T Cell Immunity.",{"slug":396,"name":397,"description":398,"image":42,"body":42,"postCount":205},"fungal-diagnostics","Fungal Diagnostics","Various methods used for the Diagnosis of Fungal Infections. ",{"slug":400,"name":401,"description":402,"image":42,"body":42,"postCount":221},"laboratory-storage-and-preservation","Laboratory Storage and Preservation","Articles about Laboratory Storage of Antimicrobial Disk, Test organisms and Equipment used for this process. ",{"slug":404,"name":405,"description":406,"image":42,"body":407,"postCount":164},"laboratory-heating-equipment","Laboratory Heating Equipment","A guide to laboratory heating equipment, including hot plates, water baths, Bunsen burners, incubators, and dry baths, and how to choose the right one for each task.","Laboratory heating equipment covers the instruments that warm, melt, incubate, or sterilize samples and media in a microbiology laboratory. Each one delivers heat differently. \n\nA hot plate gives high, direct, dry heat; a water bath gives gentle, even, wet heat up to about 100°C; a Bunsen burner gives an open flame for rapid, very high heat; an incubator holds cultures at a steady temperature over hours or days; and a dry bath heats small tubes without water. Choosing the right one depends on the temperature you need, how precise it must be, and whether the sample can tolerate direct or open-flame heat.\n\nThe articles below cover each piece of heating equipment in detail, including its parts, working principle, uses, and the mistakes that most often go wrong at the bench.",{"slug":409,"name":410,"description":411,"image":42,"body":42,"postCount":226},"laboratory-glassware","Laboratory Glassware","Posts about Laboratory Glassware. ",{"slug":413,"name":414,"description":415,"image":42,"body":42,"postCount":164},"helminths","Helminths","In this section, we are covering properties, life cycle, pathogenesis and laboratory diagnosis of Helminths\u002FHelminthic infestations. ",{"slug":417,"name":418,"description":419,"image":42,"body":42,"postCount":164},"protozoan-parasite","Protozoan Parasite","In this cluster, we are covering protozoan parasites. ",{"slug":421,"name":422,"description":423,"image":42,"body":42,"postCount":175},"tests-for-gram-positive-cocci","Biochemical Tests for Gram Positive Cocci","This is the lists of Biochemical Tests that are used for Gram Positive Cocci. ",{"slug":425,"name":426,"description":427,"image":42,"body":42,"postCount":261},"bacterial-staining-technique","Bacterial Staining Technique","Lists of various staining techniques that are used to stain bacteria. ",{"slug":429,"name":430,"description":431,"image":42,"body":42,"postCount":159},"enzyme-tests","Enzyme Tests","\u003Cp>Various Biochemical Test that are based on enzymatic activity of the microorganisms. \u003C\u002Fp>",{"slug":433,"name":434,"description":435,"image":42,"body":42,"postCount":216},"carbohydrate-utilization","Carbohydrate Utilization","\u003Cp>Various biochemical tests which are related to Carbohydrate fermentation or Utilization\u003C\u002Fp>",{"slug":437,"name":438,"description":439,"image":42,"body":42,"postCount":221},"susceptibility-based-id","Susceptibility-based ID","\u003Cp>These are susceptibility based identification test such as optochin sensitivity, bacitracin sensitivity etc. \u003C\u002Fp>",{"slug":441,"name":442,"description":443,"image":42,"body":42,"postCount":331},"microbial-metabolism","Microbial Metabolism","\u003Cp>Tests about Microbial Metabolism. \u003C\u002Fp>",{"slug":445,"name":446,"description":447,"image":42,"body":42,"postCount":226},"substrate-utilization","Substrate Utilization","\u003Cp>The test in which a non-sugar carbon\u002Fnitrogen source is used or degraded (citrate, malonate, decarboxylases, indole, PAD).\u003C\u002Fp>",{"slug":449,"name":450,"description":451,"image":42,"body":42,"postCount":387},"atypical-pneumonia","Atypical Pneumonia","\u003Cp>Organisms responsible for Atypical Pneumonia. \u003C\u002Fp>",{"slug":453,"name":454,"description":455,"image":42,"body":42,"postCount":221},"antigen","Antigen","\u003Cp>Various articles related to Antigens.\u003C\u002Fp>",{"slug":70,"name":457,"description":458,"image":42,"body":42,"postCount":243},"Innate Immunity","\u003Cp>Articles related to Innate Immunity. \u003C\u002Fp>",{"slug":460,"name":461,"description":462,"image":42,"body":42,"postCount":331},"respiratory-tract-infection","Respiratory Tract Infection","\u003Cp>In this cluster, you can see various etiological agents that causes respiratory tract infection. \u003C\u002Fp>",{"slug":464,"name":465,"description":466,"image":42,"body":42,"postCount":221},"torch-infection","TORCH Infection","\u003Cp>In this section; you can find articles related with TOCH infection. \u003C\u002Fp>",{"slug":468,"name":469,"description":470,"image":42,"body":42,"postCount":243},"microbiology-for-beginners","Microbiology for Beginners","\u003Cp>These articles are very basic articles, which will share general concepts in Microbiology. \u003C\u002Fp>",{"slug":472,"name":473,"description":474,"image":42,"body":42,"postCount":164},"dna-replication","DNA Replication","\u003Cp>Articles related to DNA and Replication of DNA. \u003C\u002Fp>",{"slug":476,"name":477,"description":478,"image":42,"body":42,"postCount":243},"genetic-code","Genetic Code","\u003Cp>Articles related to Genetic Code.\u003C\u002Fp>",{"slug":480,"name":481,"description":482,"image":42,"body":42,"postCount":221},"molecular-technique","Molecular Technique","\u003Cp>Posts related to Molecular Techniques. \u003C\u002Fp>",{"slug":484,"name":485,"description":42,"image":42,"body":42,"postCount":175},"colorimetric-assay","Colorimetric Assay ",{"slug":487,"name":488,"description":489,"image":42,"body":42,"postCount":221},"pharmaceutical-microbiology","Pharmaceutical Microbiology","\u003Cp>Various articles related to Pharmaceutical Microbiology\u003C\u002Fp>",{"slug":491,"name":492,"description":42,"image":42,"body":42,"postCount":387},"blood-and-immune-cells","Blood and Immune Cells"]