Lecture #4

Question 1

Professional APCs are

Answer 1

DC: present Ag for naive T cell and activatng them in the LN Macrophages: present Ag to effector Th1 cells B cells: present Ag to effector Th2 cells

Question 2

MHC complex in the genome

Answer 2

HLA genes on the short arm of ch6

Question 3

HLA alleles for MHC I

Answer 3

Classical: A, B, C

Non classical: E, F, G

Question 4

HLA alleles for MHC II

Answer 4

Classical: DP, DQ, DR

Non classical: DM, DO

Question 5

MHC I structure

Answer 5

Alpha chain (alpha 1, 2, 3)

Alpha 1 and alpha 2 forming the Ag binding site and alpha 3 forming the TM domain

Beta 2 microglobulin subunit (has no TM domain)

Ag binding site is a closed pocket framed by alpha helicies to fit only 8-9AA

Question 6

MHC II structure

Answer 6

Alpha and beta globulins with 2 subunits each

Alpha 1 and beta 1 form the Ag binding site, open pocket framed by alpha helicies to fit 10-20AA Ag

Alpha 2 and beta 2 have TM domains

Question 7

What are the specific AA locations on the Ag that MHC binds?

Answer 7

MHC I bind AA in position 1 and 8/9

MHC II binds AA in position 1, 4, 6, 9

Question 8

?What is the bond type between an Ag and MHC

Answer 8

H bonds

Question 9

Expression of MHC and costimulatory molecules by DC

Answer 9

DC in the tissues express very little MHC as oppose to DC in lymphoid organs

Costimulatory molecules are constituitivly expressed

Question 10

Expression of MHC and costimulatory molecules by macrophages

Answer 10

MHC expression is induced in macrophages from no expression to high expression

so does costimulatory molecules

Question 11

Expression of MHC and costimulatory molecules by B cells

Answer 11

MHC is contantly expressed at high amount and can be further induced

Costimulatory molecules are induces from zero to high expression

Question 12

Unprofessional APCs during severe inflammation

Answer 12

Fibroblast in the skin

Glial cells in the brain

Pancreatib beta cells

Question 13

All nucleated cells express maximum ___ MHC I variations

Answer 13

6

Question 14

Professional APCs express maximum ___ MHC variations

Answer 14

12

Question 15

Exibiconism

Answer 15

Continuous expression of self antigens with simultaneous presentation of tumor or viral antigens

Question 16

Endogenous antigen presentation process

Answer 16

1. Endogenous proteins or DRIPs are targeted to proteosomal degradation
2. TAP1/2 complex transpor the small peptides to the rER lumen and link them to an MHC I
3. Vesicular transport through thr Golgi and presentation on the membrane

TAP transport associated with Ag processing

DRIP defective ribosomal products

Question 17

Exoogenous antigen presentation process

Answer 17

1. Pagocytosis
2. Phagolysosome fusion and degradation
3. Endosome contain short microbial peptides
4. iMHC II is synthesized and secreted to the rER, Golgi and out on a vesicle
5. Fusion of the vesicle with the endosome
6. Invariant chain degradation and CLIP remains
7. CLIP is removed by HLA DM and DO
8. Ag is placed on to the MHC II to be presented

Question 18

Lipid Ag presentation

Answer 18

Glycolipids and lipids are presented by MHC like molecule CD1 expressed on: thymocytes, B cells, DC, hepatocytes and epithelial cells

Question 19

Glycopeptide presentation by TCR

Answer 19

TCR alpha/beta

only mono and di saccharides

TCR gamma/delta

only di and tri saccharides

Question 20

Cross presentation

Answer 20

The process of presenting exogenous (viral or tumor) antigens on MHC I

in order for the activation of naive Tc cells as well and induction of cytotoxicity

Question 21

Cross dressing

Answer 21

Occurs mainly in DC, uptake exosomes from mTEC with MHC on them and express them on the surface

Question 22

Regulation on MHC I expression

Answer 22

IFN gamma TNF alpha and lymphotoxin

Question 23

Regulation on MHC II expression

Answer 23

Increase exp: IFN gamma

Decrease exp: tumor cells, corticosteroids, prostaglandins

Question 24

MHC is…

Answer 24

Polymorphic

Polygenic

Codominantly inherited