Adaptive: Cell-mediated immunity

Question 1

What are the functions of MHC proteins?

Answer 1

-present antigen to T cells
-activate T cells
-develop T cell repertoire and tolerance (thymus)
-recognise self and non-self

-graft rejection
-involved in some autoimmune diseases

Question 2

How are naive T cells activated?

Answer 2

Signal 1: interaction between TCR and co-receptors (CD4/8) (on T cells) with MHCI/II (on APC)
Signal 2: interaction between CD28 (on T cells) with co-stimulatory molecules (eg. B7 on APC)
Signal 3: interaction between activated T cell and cytokine triggers T cell to be converted into subset

Question 3

How do cytotoxic T cells induce apoptosis?

Answer 3

-release granzymes into target cell via perforin channels (like NK cells)
-release fas ligands, which cluster target cell Fas (death) receptors together