Question

what are the effector mechanisms of CD4 and CD8 T cells?

Answer 1

The effector mechanisms of CD8 T CELLS are:

1.CD8+ T Cells downregulate the CD4 T cells generated against autoantigens and foreign antigens.

2.They inhibit proliferation of CD4 T cells and lyse vacine induced CD4 T cells thereby helping in EAE resistance.

3. CD8 T cells enhance apoptosis of autologous, superantigen-activated CD4 T cells via Fas–FasLigand interaction.

4.CD8 T cells indirectly regulate CD4 T cells by producing cytokines like IL-4,IL-10.It is through cytokines they down regulate and enhance apoptosis of CD4 T cells.

5.CD8 T cells suppress IgE by IFN-Gamma.

6.Secretes perforin, granzymes when exposed to infected somatic cells thereby killing them

7.Perforin forms pore in the cell and granzyme enters the cells triggering caspase cascade which activates apoptosis.

The effector mechanisms of CD4 T Cells :

1.CD40L is a protein ligand present in the CD4 T cell surface  is that is a member of the TNF superfamily of molecules. It binds to CD40 on antigen-presenting cells, B- cells that leads to cytokie releases

2. CD154 is another molecule that acts as a co stimulatory molecule. CD154 helps in  B cell maturation and interacts with CD40 on the B cell surface and facilitates cell-cell communication helping in class switching and antibody production.

3. Cytokine is released when CD40 on APC binds to CD40L on T cells and antigen is presented using MHC II molecule.These cytokines have two profiles, Th1 and Th 2.

Th1 is shown when macrophages act as APC, Th2 is shown when B-cells acts as APC.

4. Th1 promotes the killing efficacy of the macrophages and the helps proliferate cytotoxic CD8+ T cells.

5.Th1 promotes the production of IgG.

6.Th2 cytokines promote more of their secretion through autoregulatory function. These cytokines (IL-4, IL10,IL-13...) are used by T cells for regulatory functions also.