Lecture 16 - immune activation

Question 1

MHC class 1 vs class 2

Answer 1

MHC1

• CD8 T cells (cytotoxic T cells), virally infected cells
• HLA, B, C

MHC2

• CD4 T cells (helper T cells), antigen presenting cells
• HLA DP, DQ, DR

Question 2

What happens when people have a defect in endogenous antigen presentation

Answer 2

Some people have poor antigen processesing for virlly infected cells

• Low HLA, B,C
• have fewer CD8 t cells but normal Cd4 t cells
• get recurrent respiratory viral infections because they cannot break down the viral antigen to show that something is wrong

Question 3

Adhesion molecules

Answer 3

selectins - weak interactions, direct cell traffic around body, like velcro
-L selectin - circulating lymphocytes
-P selectin - platelets, endothelial cells to attatch neurtrophils
E-selectin - vascular endothelium. induced by pro-inflammatory cytokines

Integrins - strong cell-cell adhesion , hold cells in tissues together
-these stick to complementary ligands

Question 4

Adhesion of neutrophils

Answer 4

• neutrophils will attatch to selectins and roll down (weak binding)
• Then this will trigger integrin expression, and get stronger bindign
• then will migrate inbetween cells

Question 5

Lymphocyte activation - ANtigen presenting cells

Answer 5

Antigen presenting cells
1st signal - cd4-mhc2
2nd signal - ligands ICAM-3 is on APC, and this matches to LFA-1
also need costimulators

e. g if bacteria is broken down, then this gets put on the mhc2 on APC, however danger signals (PAMPs) will upregulate B7 molecule
- b7 molecule will match CD28 on T helper cell and then give signal to go on to become activated

Question 6

B cell activation

Answer 6

For b cells to become activated they need help from T helper cells

• B cells take up antigen, process this and put on MHC2
• If get CD40 on b cell match with CD40-L on t cell, then will go on to upregulate B7 in b cell
• then if cd28 matches to b7 - then will get cytokines produced from t helper cell
• this will activate B cell