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Immunology > MHC and Antigen Presentation to T cells > Flashcards

MHC and Antigen Presentation to T cells Flashcards

1
Q

T cell receptor (TCR) is composed of 2 polypeptide chains ____ and ____

which are made up of ____ and ____ regions

A

alpha and beta

constant and variable

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2
Q

the genes coding for TCR, CD3, CD4, CD8, and MHC are members of the ____ super family

A

Ig

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3
Q

unlike Abs, TCRs do not recognize native antigen, but can only bind processed Ag presented in associated with ____ molecules

A

MHC

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4
Q

unlike BCR (Abs), TCR are never produced in a ______ form

A

secreted

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5
Q

the ____ region of alpha and beta chains of TCR constitute the Ag-binding site

A

variable

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6
Q

some unconventional T cells express a TCR consisting of ____ and ____ chains

A

gamma and delta

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7
Q

gamma/delta T cells have a broader specificity for unconventional Ag such as ____ and ____

(don’t need APCs for activation)

A

HSPs and phospholipids

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8
Q

TCR is associated with nearby ___ signaling complexes

A

CD3

composed of gamma, delta, and epsilon chains

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9
Q

____ Ags are presented to T cells in association with MHC molecules

A

peptide

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10
Q

class I MHC is expressed on all

A

nucleated cells

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11
Q

class II is expressed on

A

professional Ag-presenting cells (DCs, mast cells, B cells)

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12
Q

in class I MHC, what chain(s) contributes to peptide binding groove

A

only alpha chain

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13
Q

in class II MHC, what chain(s) contributes to peptide binding groove

A

both alpha and beta

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14
Q

what MHC binds smaller peptides

A

MHC class I

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15
Q

CD4 (Th cells) recognize Ags presented by class ___ MHC

A

class II

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16
Q

CD8 (cytotoxic T cell) recognize Ags presented by class ____ MHC

A

class I

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17
Q

MHC/HLA loci is located on Chromosome

A

6

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18
Q

______ ______ refers to a discotinuous genetic variation resulting in the occurrence of several different types of individual molecules

A

molecular polymorphism

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19
Q

class I genes (HLA-A, -B, -C) encode a polymorphic heavy chain which is expressed together with beta2-microglobulin and on the surface of all nucleated cells for Ag recognition by _____ T cells

A

CD8+

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20
Q

class II genes (HLA-DP, -DR, -DQ) which are expressed on the surface as alpha and beta polymorphic polypeptide chains on APCs for Ag recognition by _____ T cells

A

CD4+

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21
Q

in class I molecules, the ____ chain is glycosylated

A

alpha

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22
Q

in class II molecules, the ____ chain is glycosylated

A

both alpha and beta

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23
Q

_____ ______ on the peptides bind to residues in the class I and class II grooves and vary for different MHC alleles

A

anchor residues

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24
Q

the cleft of class I molecules are _____ whereas the cleft of class II molecules are _____

A

closed

open

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25
Q

HLA class II molecules are expressed on

A

professional APCs (e.g. B cells, dendritic cells, and macrophages)

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26
Q

HLA class I molecules are expressed on

A

all nucleated cells

27
Q

expression of MHC class I and/or II molecules is modulated by

A

cytokines

28
Q

peptides that bind to class I MHC molecules are derived from ______ microbes that have infected host cells

A

intracellular

endogenous pathway

29
Q

peptides that bind to class I MHC are recognized by what cells

A

CD*+ cytotoxic T cells

30
Q

Ags and extracellular pathogens taken from the environment are primarily presented on class ____ MHC molecules and presented to what cells?

A

II

CD4+ helper T cells

31
Q

function of dendritic cells as APC

A

naive T cell activation: clonal expansion and differentiation into effector T cells

32
Q

function of macrophages as APC

A

effector T cell response: macrophage activation (cell-mediated immunity)

33
Q

function of B cell as APC

A

effector T cell response: B cell activation and antibody production (humoral immunity)

34
Q

_____ is a costimulatory protein found on professional APCs and binds to its ligand ______ which is found on T-cells and is required for coactivation

A

CD40

CD40L

35
Q

DCs expression of Class II MHC

A

constitutive

36
Q

Macrophage expression of class II MHC

A

low; induced by IFN-gamma

37
Q

B lymphocyte expression of class II MHC

A

constitutive; induced by IL-4

38
Q

Ags that enter the blood stream are captured by APCs in

A

the spleen

39
Q

APCs don’t live in ______ but do live in ______

A

lymph nodes

spleen

40
Q

activated NK cells produce ____ during innate immune reactions; this stimulates _____ expression on APCs and thus enhances Ag presentation and activation of CD4+ and CD8+ T cells

A

IFN-gamma

MHC

41
Q

B cells require _____ for isotype switching from IgM

A

CD40/CD40L interaction

42
Q

how do T cells recognize antigens

A

recognize only linear peptides

conformation is lost during enzymatic processing of protein Ags into peptides

43
Q

T cells recognize cell-associated antigens, not _____ antigens

A

soluble

44
Q

MHC class II molecules display peptides that are taken up from ______ environment of APCs by mechanisms of either pinocytosis (DCs and B cells) or phagocytosis (macrophages)

A

extracellular

45
Q

MHC class I molecules present peptides generated in the proteasome from ______ proteins including proteins from ______ pathogens

A

cytosolic

intracellular

46
Q

CD4+ T cells recognize what type of Ags acquired by professional APCs?

A

extracellular

47
Q

CD8+ T cells recognize what type of Ags?

A

Ags derived from intracellular proteins

48
Q

class I MHC pathway

A
  1. production of proteins in the cytosol (virus)
  2. virus peptides are tagged by ubiquinase and sent to proteosome for proteolytic degradation of proteins
  3. transport of peptides from cytosol to ER
  4. assembly of peptide-MHC class I complexes in ER
  5. peptide-MHC class I complex is sent to Golgi Apparatus to be vesicular
  6. surface expression of peptide-MHC class I complexes
49
Q

TAP

A

transporter to get peptides into ER

50
Q

class II MHC pathway

A
  1. uptake of extracellular proteins into vesicular compartments of APC
  2. processing of internalized proteins in endosomal/lysosomal vesicles (forms phagolysosome)
  3. synthesis and transport of class II MHC molecules from ER to endosome
  4. association of processed peptides with class II MHC molecules in vesicles
  5. expression of peptide-MHC complexes on cell surface
51
Q

there are a lot of self peptides synthesized in the ER which are prevented from binding to class II MHC by the ______ chain

A

invarient

52
Q

protein HLA-DM removes the invariant chain and allows the ______ of extracellular Ags into class II MHC

A

loading

53
Q

the HLA-DM editing mechanism works to ensure the presentation of only the protein fragments most relevant for eliciting an immune response.

HLA-DM has 3 major functions:

HLA-DM causes the dissociation of ______ from the peptide binding groove of MHC II

HLA-DM stabilizes and prevents ______ of the empty MHC II

HLA-DM facilitates the binding of Ag fragments to the ______ stabilized binding groove

A

CLIP

degradation

open

54
Q

CLIP is a protein that binds MHC class II and acts as a ______ so nothing else binds to it

A

placeholder

55
Q

cross presentation

A

excellular pathogens get presented to CD8+ T cells via MHC-II

56
Q

cross-presentation pathway

A
  1. some extracellular pathogens brought in b phagocytosis leak into the cytoplasm and are treated as intracellular pathogen
  2. gets tagged by ubiquitin
  3. digested by proteosome
  4. transport of peptides through TAP into ER
  5. assembly of peptide-MCH I complex in ER
  6. exocytic vesicle allows for surface expression of peptide-MHC I complex
57
Q

immunodominant peptides:

immunodominant peptides are obtained by ______ available in the cell

the peptides bind best to the available class I and II MHC molecules

thus, immune responses will be generated against ______ Ags based on the available proteases and MHC molecules

A

proteases

dominant Ags

58
Q

why aren’t erythrocytes which don’t express class I MHC not destroyed by NK cells

A

NK cells spare cells that express “markers of normal self” in the form of MHC class I molecules, and eliminate them when these markers are absent or insufficiently expressed

59
Q

CD47

A

glycoprotein consistently expressed on RBCs that serves as a marker of self

60
Q

CD47 binds to

A

inhibitory receptor on NK cells

61
Q

activated Th1 cells help ______ to get rid of ______ microbes and help development of cytotoxic T cells

A

macrophages

intracellular

62
Q

cytokine IFN-gamma produced by ______ activated macrophages

A

Th1 cells

also NK cells

63
Q

activated Th2 cells are mainly involved in responses against _______ microbes helping _______ cells to develop into memory cells and plasma cells that produce antibodies

A

extracellular

B

64
Q

cytokine IL-4 is produced by _______ cells and is important for ______ cell proliferation

A

Th2

B

Immunology (23 decks)

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