CD4 + T lymphocytes
المؤلف:
Stuart H. Ralston , Ian D Penman, Mark W J Strachan , Richard Hobson
المصدر:
Davidsons Principles and Practice of Medicine
الجزء والصفحة:
24th E , p67
2025-01-08
940
These cells recognise peptides presented on HLA class II molecules (HLA-DR, HLA-DP and HLA-DQ) and have mainly immunoregulatory functions. They produce cytokines and provide co-stimulatory signals that support the activation of CD8 + T lymphocytes and assist the production of mature antibody by B cells. In addition, their close interaction with phagocytes determines cytokine production by both cell types. CD4 lymphocytes can be further subdivided into subsets on the basis of the cytokines they produce:
- Th1 (T-helper) cells typically produce IL-2, IFN-γ and TNF-α, and support the development of delayed-type hypersensitivity responses.
- Th2 cells typically produce IL-4, IL-5, IL-10 and IL-13, and promote allergic responses.
- T-regulatory cells (T-regs) are a further subset of specialised CD4 + lymphocytes that are important in actively suppressing activation of other cells and preventing autoimmune disease. They produce cytokines such as TGF-β and IL-10.
- Th17 cells are pro-inflammatory cells defined by their production of IL-17. They are related to regulatory T cells. Th17 cells have a key role in defense against extracellular bacteria and fungi. They also have a role in the development of autoimmune disease.
T-cell activation is regulated by a balance between co-stimulatory molecules , the second signal required for activation, and inhibitory molecules that down-regulate T-cell activity. One such inhibitory molecule, CTLA4, has been harnessed therapeutically in the form of abatacept, which is a fusion protein comprised of the Fc fragment of immunoglobulin linked to CTLA4. This is used to inhibit T-cell activation in rheumatoid arthritis and solid organ transplantation.
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