9. T cell mediated immunity

Question 1

differences between B and T cells in antigen recognition

Answer 1

native B cells can recognise antigen

native T cells can only recognise APC

Question 2

T cell receptor

Answer 2

two polypeptide alphaß chains

disulfide linked dimer

small cytoplasmic tail

member of immunoglobin super family

one antigen combining site (B cells have two)

Question 3

what do CD4 T helper cells help with

what do CD8 cytotoxic T cells do

Answer 3

B cells- Ab production (virus and bacteria)

macrophages- phagocytosis and killing (bacteria)

CD8 kill infected cells (virus)

Question 4

Answer 4

Question 5

HLA

Answer 5

Human leukocyte antigen

human version of MHC

Question 6

MHC class I structure

Answer 6

• large alpha chain non covalently associated with beta 2 microglobulin
• expressed on ALL nucleated cells
• presents to Tc cells with CD8 co receptors that bind to alpha 3 chain
• allows any infecte cell to be killed

Question 7

MHC class II structure

Answer 7

two polypeptide chains of alpha nad beta chains

present to Th cells with CD4 co receptor binds to beta 2

expressed by MACROPHAGES, OTHER APC, B CELLS

-> require activation by Th

Question 8

TCR interaction

Answer 8

Question 9

binding

Answer 9

Question 10

processing and presenting of antigen for HLA class I

Answer 10

1. protein antigens in cytosol cleaved by proteasome
2. peptides transferred into ER via peptide transporter proteins
3. peptides associate with newly synthesised HLA I
4. peptide/ HLA complex transported to cell surface for recognition by Tc

Question 11

processing and presenting of antigen for HLA class II

Answer 11

1. endocytosis of exogenous antigen-> vesicle
2. enzymes entering vesicles degrade antigen
3. newly synthesised HLA II with invariant chain in ER transported to vesicle
4. invariant chain degraded, antigen peptides associate with HLA II
5. peptide/ HLA II complex transported to cell surface

Question 12

the importance of an invariant chain in antigen presenting to HLA II

note about HLA I

Answer 12

blocks peptides from binding in the ER

most microbes do not infect dendritic cells to produce class I, have cross preseneting/ cross priming where exogenous antigens diverted into class I pathway for presentation to CD8

Question 13

Answer 13

Question 14

how do dendritic cells ensure activation of T cells

Answer 14

1st signal: B7 molecules on cells with pathogen

2nd signal: CD28 to activate

Question 15

what signal determined T cell differentiation

Answer 15

polarising signal: PAMPs, tissue factors, CD40 stimulation