T and B cell activation

Question 1

APC cell types

Answer 1

B-cells, dendritic cells, Langerhans cells, macrophages

Question 2

Steps for APC to present antigen on MHC

Answer 2

Samples antigen, processes antigen, migrates to draining lymph node, antigen presented on MHC-I/II

Question 3

Activation of CD4+ T-cell

Answer 3

Signal 1: antigen presented on MHC-II, recognized by TCR on CD4+ T-cell
Signal 2: B7 on dendritic cell binds to CD28 on naive T-cell
T-cell activates and produces cytokines

Question 4

Activation of CD8+ T-cell

Answer 4

Signal 1: Endogenous or cross-presented on MHC-I to CD8+ T-cell
Signal 2: B7 on dendritic cell binds to CD28 on naive T-cell,
Cytotoxic T cell activates and able to recognize and kill virus-infected cell.

Question 5

Activation of B-cell

Answer 5

1. CD4+ T-cell activated
2. B-cell presents foreign antigen on MHC-II
3. Recognized by TCR on helper T-cell & secretes cytokines that determine Ig class switching
4. B-cell activates, undergoes class switching, affinity maturation, and antibody production

Question 6

Functions of antibodies

Answer 6

1. Promote phagocytosis
2. Prevent bacterial adherence
3. Activate complement, enhance opsonization and lysis