53-MHC and Antigen Presentation Flashcards Preview

Immunology > 53-MHC and Antigen Presentation > Flashcards

Flashcards in 53-MHC and Antigen Presentation Deck (44)
1

T cells

effector cells of adaptive immune response, 3 types

2

CD8 t cell

t killer cells
recognize infected cells and kill them

3

CD4 t cell

t helper cells
regulate function of other cells and release cytokines

4

gamma delta t cell

like innate cells, mucosal immunity

5

activation of T cell

requires 3 signals
activation
survival
differentiation

6

signal 1 for t cell

activation
from TCR
activation of TCR by antigen/MHC

7

signal 2 for t cell

survival
from costimulatory receptors of antigen presenting cells
CD28 binding to B7.1 and B7.2

8

signal 3 for t cell

differentiation
from cytokines produced by antigen presenting cells

9

antigens

proteins or large polysaccarides that are recognized by T cells using TCR

10

epitopes

small portion of antigens recognized by TCR

11

TCR/MHC interactions

required for T cell activation, need 10-20 interactions, naïve cells need more

12

where are MHC class 1 found

nucleated cells
NOT RBC or platelets

13

MHC class 1 activate what

CD8 t killer to eliminate pathogens

14

where are MHC class 2

antigen presenting cells
macrophages
B cells
dendritic cells

15

MHC class 2 activate what

CD4 t helper to control adaptive immune response

16

MHC class 1 peptides

intracellular (mostly cytosolic proteins, some ER)
dendritic make extracellular

17

MHC class 2 peptides

extracellular
dendritic make intracellular

18

MHC class 1 structure

2 subunits
alpha-binding
beta 2 microglobulin-stabilize
bind short amino acids 8-10

19

anchor residues

amino acids on end that bind to MHC

20

loading MHC class 1

-chaperone calnexin facilitates forming MHC/b2microglobulin
-transfer to chaperone calreticulin/ERp57/tapasin that interacts with TAP
-peptides produced in cytoplasm and transferred to ER with TAP complex
-peptides cleaved to 8-10 using ERAAP protease and loaded onto MHC class 1
-released after high affinity peptide is loaded

21

viruses inhibiting MHC class 1

encode for protein to inhibit MHC class 1
evade CD8 T killer

22

combat viral suppression of MHC class 1

NK cells recognize cells with low MHC class 1 and kill them
(presence of receptors on NK that recognize MHC class 1 and suppress NK function)

23

loading MHC class 2

extracellular- pathogens loaded by phagocytosis, non specific antigens loaded by macropinocytosis
intracellular-loaded by autophagy

24

MHC class 2 structure

2 proteins: alpha and beta which make peptide binding cleft
bind loner peptides, 12-20 amino acids

25

MHC class 2 binding peptides

MHC class 2 made in ER and binds invariant chain then transported to endosome
Activation of antigen presenting cell acidifies endosome degrading invariant chain and proteins
peptides loaded onto MHC class 2 by HLA-DM

26

pathogen superantigens

bind TCR and MHC
from bacteria, virus, mycoplasmas
cause atypical activation of t cells and cytokines
create systemic toxicity and immune suppression needed for microbial pathogenicity

Septic Shock

27

CD4 T cell activation

different function depending on antigen presenting cell
dendritic-activate naive t cell
macrophage-cell mediated immunity
b cell-humoral immunity

28

Dendritic cell activating CD4

activate naive T cell for clonal expansion and differentiation into effector T cell

29

Macrophage activating Cd4

macrophage activation, activation of effector CD4 T cells at infection and inflammation
cell mediated immunity

30

B cell activating CD4

b cell activation and antibody production, humoral immunity

31

cross presentation

dendritic cells present extracellular on class 1 and intracellular on class 2
critical for activation of naive CD8 T cells

32

DC licensing

activation of dendritic cells by CD4 T cells

33

MHC locus

contains 200 genes
most gene rich regions in genome
on chromosome 6
involved in antigen presentation and peptide loading

34

MHC class 1 genes

HLA A, B, C

35

MHC class 2 genes

DR, DQ, DP

36

polymorphism

multiple alleles for same gene
MHC are most polymorphic genes in humans
Class 1 higher number of alleles than Class 2

37

polygeny

having multiple genes with same function

38

function of polymorphism and polygeny

increase potential number of peptides that can be bound by MHC

39

MHC haplotype

combination of MHC genes on single chromosome
inherited as a single gene
new MHC alleles and haplotype arise from point mutations

40

Major diversity in MHC is where

peptide binding groove/cleft

41

function of diversity in MHC peptide binding groove

each allele can bind peptide with different anchor residue
increase total pool of peptides that can be bound

42

autoimmune disorders

linked to specific haplotypes of MHC Class 2

43

presence of pathogenic haplotype

does not cause disease but increases disease susceptibility

44

why does pathogenic haplotype increase disease susceptibility

better able to bind self antigens, induce cytokine production, promote polymorphisms that increase MHC or protein expression