Cell Mediated Immunity

By Acharya Tankeshwar •  Updated: 05/21/22 •  4 min read

Two components of the adaptive immune response are cell-mediated immunity and antibody-mediated (humoral) immunity. The cell-mediated arm consists primarily of T lymphocytes (e.g., helper T cells and cytotoxic T cells).

Functions of Cell-Mediated Immunity

  1. Cell-mediated immunity protects the host against several intracellular bacteria (such as Mycobacterium tuberculosis, atypical mycobacteria, Legionella pneumophila, and Listeria monocytogenes), fungi, and parasites. The cell-mediated immune response is involved in granuloma formation.  Granuloma formation is seen in major systemic fungal diseases such as coccidiodomycosis, histoplasmosis, and blastomycosis.
  2. Cell-mediated immunity kills virus-infected cells and altered self-cells (tumor cells). Cytotoxic T cells are responsible for killing virus-infected cells.
  3. Graft and tumor rejection
  4. Regulation of antibody response (help and suppression)
  5. Allergy (hypersensitivity). For example, poison oak

Reduced cell-mediated immunity predisposes people to infections with the following pathogens;

  1. Nocardia asteroides
  2. Mycobacterium leprae (in people with lepromatous leprosy the cell-mediated response to M. leprae is defective)
  3. Rhodococcus equi
  4. Herpes simplex virus (HSV): Suppression of cell-mediated immunity often results in reactivation, spread, and severe infections with HSV.
  5. Varicella-zoster virus (VZV): Suppression of cell-mediated immunity reactivate the VZV latently residing in infected cells and causes zoster (shingles).
  6. Cytomegalovirus: Suppression of cell-mediated immunity can cause systemic infections with cytomegalovirus.
  7. Epstein-Barr virus (EBV): Reduced cell-mediated immunity predisposes to the uncontrolled growth of the EBV-infected cells.
  8. Fungal infections: Suppression of cell-mediated immune response can lead to reactivation and dissemination of asymptomatic fungal infections and opportunistic fungal infections. For example, a disease caused by Cryptococcus neoformans occurs mainly in patients with reduced cell-mediated immunity, especially AIDS patients. Reduced cell-mediated immunity also predisposes to disseminated disease caused by systemic fungi, such as Histoplasma and Coccidioides.
  9. Toxoplasma gondii: In patients with reduced cell-mediated immunity (e.g., patients with AIDS), life-threatening toxoplasmosis, primarily encephalitis can occur. Cell-mediated immunity is responsible to limit the spread of tachyzoites of T. gondii.

Cell-mediated immunity is antibody antibody-independent immunity, mediated by TH1 cells.
Examples: Type-IV Hypersensitivity responses against Mycobacterium tuberculosis and other intracellular pathogens.

Macrophage Activation: IFN-gamma, secreted by TH1 cells, activates macrophages.

Acharya Tankeshwar

Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. As an asst. professor, I am teaching microbiology and immunology to medical and nursing students at PAHS, Nepal. I have been working as a microbiologist at Patan hospital for more than 10 years.

One response to “Cell Mediated Immunity”

  1. Sweetcollins says:

    Hi , I am Collins I need more clarifications on the CD4, CD8…

We love to get your feedback. Share your queries or comments

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: