2.2 T-cells and Cell Mediated Immunity

Question 1

How do naive T cells exit the circulation and enter lymph nodes?

Answer 1

High Endothelial Venules (HEVs)

Question 2

What is the third law of immunology?

Answer 2

CD8 only look at MHC I peptides (intracellular infection)
CD4 only look at MHC II peptides (extracellular infection)

Question 3

Describe the CD3 complex

Answer 3

CD3 complex is required to relay the TCR signal
Signal delivered by CD3 proteins
Phosphorylate the receptor and drives cell signalling cascade
Leads to T cell activation

Question 4

What is Cyclosporin?

Answer 4

Immunosupressive drug used to treat immune-mediated disease

Question 5

What activates naive T cells?

Answer 5

Antigen signal (TCL with MHC)

Danger signal (CD80 + CD86 with CD28)

Question 6

What happens when naive T cells are activated?

Answer 6

Secrete IL-2 which acts on its own recepors to induce proliferation

Clonal expansion

Question 7

What do naive T cells differentiate into?

Answer 7

CD8 cells = Killer cells (cytotoxic)
CD4 cells = Helper or Regulatory cells

Question 8

What do B cells and T cells produce?

Answer 8

B cells produce ANTIBODY
T cells produce CYTOKINES

Question 9

What is a cytokine?

Answer 9

‘Immunlogical hormones’ that influence the function of other cells for immune defence

Question 10

What are the functions of interleukins 2, 4, 10?

Answer 10

IL-2: T cell proliferation
IL-4: B cell growth factir
IL-10: immunosuppression

Question 11

What is the function of interferon-gamma?

Answer 11

INF-gamma: macrophage activating factor

Question 12

What is the function of TNF-alpha?

Answer 12

Tumor Necrosis Factor
TNF-alpha: cell killing

Question 13

How do CD8 cells kill infected cells?

Answer 13

• Leave 2º lymphoid tissues to reenter circulation
• Alter receptors to target inflamed endothelium
• Release:
  ~ cytokines
  ~ granules
  ~ FasL/Fas interaction

Question 14

How do granules cause apoptosis?

Answer 14

Degranulation
Perforin pore = entry of granzymes
Caspase cascade
Apoptosis

Question 15

What are the two main types of CD4 T-helper cells?

Answer 15

Macrophages are friends with Th1 cells
B cells are friends with Th2 cells

Mutually beneficial - Th cells help their ‘friends’ by secreting cytokines that enhance their activity.

Question 16

What do CD4 Th1 cells do?

Answer 16

Release IFN-gamma to super-activate macrophages

Respiratory burst and lysosomal digestion

Question 17

What do CD4 Th2 cells do?

Answer 17

Produce cytokines to tell B cells which type of antibody to secrete (IgG, IgA, IgE)

No Th2 = IgM only

Question 18

What do regulatory T cells do?

Answer 18

‘Military police’ - produce immunosuppressive cytokines (calms down immune response to check if the appropriate actions are taken and prevent attack of own cells)

Question 19

What do memory T cells do?

Answer 19

‘Reseverves’ for long term immunity

Express the same homing receptors as naive T cells (HEVs) and go back to immune surveillance.