Difference between B Cells and T Cells

Last updated on June 1st, 2021

T cells and B cells are white blood cells that are important cells for adaptive immunity. Like all blood cells, they are made in the bone marrow. While B-cells mature in the bone marrow, T-cells travel through the bloodstream to the thymus (a small organ between the lungs and behind the sternum) and mature there. Broadly speaking T cells can be divided into two different types, ‘killer T-cells’ and ‘helper T-cells’.

Regulatory T cells (also called Tregs) are another types of T cells.
Tregs have a role in regulating or suppressing other cells in the immune system. 2018 Nobel prize in Physiology and Medicine is related to negative immune regulation. Find more in nobelprize.org

Killer T cells also known as cytotoxic T cells (CTL) hunt down and destroy cells that are infected with germs or that have become cancerous while helper T cells help B cells to make antibodies. T helper (TH) cells express CD4 molecules and are restricted to recognize antigen bound to class II MHC molecules, whereas T cytotoxic (TC) cells express CD8 and are restricted to recognize antigen bound to class I MHC molecules. Cytotoxic T cells kill cells that are infected with viruses or altered self-cell with toxic mediators (perforin and granzymes).

B cells are major cells of humoral (antibody mediated) immunity, effector B cells (plasma cells) produce antibodies which circulate, capture and destroy antigens.

Helper T cells and B Cell Interactions (Source: Kubay Immunology)

Circulating helper T cells recognize exogenous antigen and produce cytokines. Two major groups of helper T cells are known as Th1 and Th2 cells. Th1 cells predominantly produce interferon-g (IFN-g), which promotes cell-mediated immune mechanisms. Th2 cells produce mostly interleukin-4 (IL-4), which promotes humoral immunity by activating B cells.

When a naïve (virgin) B cell first encounters the antigen that matches its membrane bound antibody, the binding of the antigen to the antibody causes the cell to divide rapidly (clonal expansion); its progeny differentiate into memory B cells and effector B cells called plasma cells. Plasma cells secrete antibodies which acts as major effector molecules of humoral immunity.

Some of the major differences of B Cells and T Cells is tabulated below:

Features B Cells T Cells
Maturation Bone Marrow  (Bursal equivalent) Thymus
Involvement of MHC moleculesNone requiredRequired to display processed antigen
Recognition of Antigen
B Cells can recognize and bind to soluble antigen. T-cell receptor (TCR) does not recognize free antigen. T cells can recognize an antigen only when it is associated with self MHC molecule on the surface of a self-cell (either an antigen-presenting cell or altered self cell or on virus infected cell and graft).  
Chemical nature of antigen
B cells recognizes an enormous variety of antigens such as Protein, polysaccharide, lipid.

T cells recognizes protein epitopes displayed together with MHC molecules on self-cells , but some lipids and glycolipids pare presented on MHC-like molecules.
Interaction with antigenInvolves binary complex of membrane Immunoglobulin and AntigenInvolves ternary complex of T-cell receptor, Antigen and MHC molecule

Epitope properties Accessible, hydrophilic, mobile peptides containing sequential or nonsequential amino acids

Internal linear peptides produced by processing of antigen and bound to MHC molecules
Antigen Specificity Antigen specificity of each B cell is determined by the membrane-bound antigen-binding receptor (antibody) expressed by the cell. Antigenic specificity of T Cells is determined by antigen-binding T-cell receptor (TCR) on T Cells. TCR genes is capable of generating on the order of 10^9 unique antigenic specificities.  
Peripheral Blood 10-15% of total lymphocytes 70-80% of total lymphocytes
Antigen recognition receptors Membrane-bound immunoglobulin (IgM or IgD complexed with Igα /Igβ) molecules serves as receptors for antigen.

T cell receptors (TCR) complexed with CD3 (signal-transduction element of T-cell receptor)  
CD markers CD32/FcγRII (Receptor for Fc region of IgG), CD35 or CR1 Receptor for complement (C3b) and CD40 (Signal transduction)CD3, CD4 (adhesion molecule that binds to class II MHC molecules; signal transduction),
CD8 (adhesion molecule that binds to class I MHC molecules; signal transduction), CD28 (receptor for co-stimulatory B7 molecule on antigen-presenting cells), CD45 (a signal-transduction molecule)

References and further reading:

About Acharya Tankeshwar 476 Articles
Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please mention in the comments below.