🌞 T Cell Subsets and Function

Question 1

What is the function of CD8+ cytotoxic T cells?

Answer 1

directly kill infected/tumour cells

Question 2

How do cytotoxic T cells kill infected cells?

Answer 2

1. perforin-granzyme pathway
   pores → granzyme entry → induce pop
2. Fas-FasL pathway
   expresses FasL → binds Fas (CD95) recep on target cell →trigger death recepor path → apoptosis

Question 3

What are the key effector molecules used by cytotoxic T cells?

Answer 3

• perforin
• granzyme
• Cks (IFN-g → inc MHC expression, MP activ // TNF-a → pro-inflammatory, induce apoptosis)
• Fas ligand (FasL)

Question 4

What is the role of CD4+ helper T cells in coordinating immune responses?

Answer 4

‘directors’ of the IR thru direct binding + ck prod

• stim B cells → Ab prod
• memory CD4+ cells → LT immunity
• activates CD8+ (binds APCs → upregs B7 expression → enhances co-stim signal #2)

Question 5

How do Th cells help B cell responses?

Answer 5

Th cells secrete ck + display costim mols → stim B cells
→ proliferation
→ differentiate → secrete Ab
→ class switch

Question 6

How do regulatory T cells suppress immune responses?

Answer 6

• inhibitory Ck
• bind APC B7 receptors → prevent co-stim → prev T cell activ
• other inhibitory mols e.g. CAMP → suppress T cell signalling paths
• induce T cell apop (perforin + granzyme)

Question 7

What are memory T cells and what is their role in immunity?

Answer 7

class of T cells that persist in body → provide LT immuniy

mount stronger + faster + longer IR upon rexposure, even when 2nd viral load = smaller