T Cell Activation and Memory

Question 1

What binds for costimulation during T cell activation?

Answer 1

CD28 (from T cells) binds to CD80/CD86 (APC)

Question 2

What are the different CD4+ T cell subsets?

Answer 2

• Th1
• Th2
• Th17
• Tfh
• Treg

Question 3

What does Th1 do?

Answer 3

Activates macrophages (via IFN-y) and promotes phago-lysosome fusion

Question 4

What does Th2 do?

Answer 4

Helps B cells class-switch to IgE and activates eosinophils for anti-parasitic defence

Question 5

What does Th17 do?

Answer 5

Recruits neutrophils to mucosal sites

Question 6

Other than disruption of antigen presentation by M. Tb, what are two mechanisms that can disrupt T cell responses?

Answer 6

1. Epstein Barr virus (Herpesvirus) inhibits costimulatory signal production by interference with CD80/CD86 expression. It also produces viral IL-10 cytokine to suppress T cell differentiation
2. Chronic infections (e.g. HIV/HCV) can induce T cell exhaustion through persistent antigen exposure. Leads to PD-1 expression and hypo(low)responsiveness

Question 7

What is PD-1?

Answer 7

A negative/down regulator of T cell activation and proliferation

Question 8

What is the primary function of central memory T cells?

Answer 8

• Don’t respond instantly to reinfection, but rapidly proliferate upon reinfection
• Act as a reservoir for secondary effector responses
• Differentiate into effector T cells (CD4 or CD8) upon reinfection

Question 9

What is the primary function of effector memory T cells?

Answer 9

• They are the first responders in peripheral tissue, providing rapid protection through the immediate production of effector molecules
• Crucial for protection at entry sites of infection

Question 10

What is the function of tissue-resident memory T cells?

Answer 10

• Provide immediate, localised protection at infection sites
• Can rapidly recruit other immune cells via cytokine release (e.g. IFN-y)
• Essential for mucosal/barrier immunity, and protection against recurrent localised infections

Question 11

What are stem cell-like memory T cells?

Answer 11

• Self renewing, multipotent memory T cells that can differentiate into central memory, effector memory or effector T cells
• Act as a reservoir for long-term memory maintenance (longest lived memory population)

Question 12

Which memory T cells have immediate effector function?

Answer 12

Effector and tissue-resident memory T cells.
Cytokine secretion and cytotoxicity