Lecture 8: Activation Of Adaptive Immunity

Question 1

Wha cell type presents Ag to naive T cells?

Answer 1

DCs

Question 2

What cell type presents Ag to activated effector T cells?

Answer 2

Macrophages and B cells

Question 3

What HLA regions are found in MHC class II?

Answer 3

DP, DQ, DR

Question 4

What HLA regions are found in MHC class I?

Answer 4

A, B, C

Question 5

HLA genes are highly ___________ and have ____________ expression

Answer 5

Polymorphic; Co-dominant

Question 6

The total _____ genes encoding HLA are in each individual: _____ HLA genes class I (A, B, C) X 2 (mother and father) = _____ genes

Answer 6

6; 3; 6

Question 7

What does it mean that HLA genes are polymorphic and why is this important?

Answer 7

It means that many different alleles are present in population.

This ensures that different individuals are able to present and respond to different microbial peptides

Question 8

What does it mean that HLA genes have co-dominant expression and what is the significance of this?

Answer 8

It means both parental alleles of each MHC genes are expressed

It increases number of different MHC molecules that can present peptides to T cells

Question 9

Do T cells express MHC class II?

Answer 9

No! Only professional APCs express class II MHC

Question 10

Class I MHC molecules have a small __________ for protein fragments

Answer 10

Groove

Question 11

Peptides that are presented within class I MHC are ______ - _____ AAs long

Answer 11

8-11

Question 12

Humans have 3 genes encoding class I MHC: HLA-___, HLA-_____, HLA-_____

Answer 12

HLA-A
HLA-B
HLA-C

Question 13

Class I HLA binds another protein called what?

Answer 13

Beta2-microglobulin

Question 14

Class I MHC presents endogenously processed peptides only for CD___ T cells

Answer 14

CD8+

Question 15

Peptide Ags noncovalently interact with both class I MHC via the ______ and _____ domains

Answer 15

Alpha 1 and alpha 2

Question 16

_______ stabilizes interaction of TCR with class I MHC molecule

Answer 16

CD8+

Question 17

What does CD in CD4 and CD8 stand for?

Answer 17

Cluster of differentiation

Question 18

What does HLA stand for?

Answer 18

Human leukocyte Ag

Question 19

Class I MHC display on the surface protein fragments manufactured by the cells. From immunologic standpoint there are ________ proteins. They are encoded by ________ and ________ pathogens which infected the cell

Answer 19

Endogenous; viruses; intracellular

Question 20

What is the process of peptide loading onto MHC class I?

Answer 20

Intracellular Ag is processed in proteosome, the peptides generated are carried into the ER using TAP1 and TAP2 and are then loaded onto MHC class I and sent to the cell surface

Question 21

Class II MHC are highly ____________ - many different versions exist!

Answer 21

Polymorphic

Question 22

Peptides that bind class II MHC are longer, about _____-____ AAs long

Answer 22

13-25

Question 23

What is the process of class II MHC loading?

Answer 23

1) Extracellular Ags are taken up by professional APCs through phagocytosis, receptor-mediated endocytosis or pinocytosis
2) Peptide s produced in phagolysosome
3) Peptide binding by MHC class II and presented on cell surface

No empty MHC molecules are displayed on the surface of APCs

Question 24

When class II MHC is synthesized in ER, it binds the 3rd protein called the _____________ chain

Answer 24

Invariant chain

Never expressed on the cell surface

Question 25

What is the significance of the class II MHC molecule binding the invariant chain?

Answer 25

ITT sits in the groove of the MHC class II and prevents MHC class II to bind the cell's own proteins in ER but instead only those from outside

Question 26

Invariant chain, a part called _______ is removed by another protein termed HLA-____ and MHC is loaded with Ags in endosomes

Answer 26

CLIP; HLA-DM

Question 27

MHC receptors have a broad specificity. What is the significance of this?

Answer 27

Many different peptides can bind to the same MHC molecule

Question 28

MHC receptors have a very slow off-rate. What is the significance of this?

Answer 28

MHC molecule displays bound peptide for long enough to be located by T cell

Question 29

What is cross-presentation?

Answer 29

Ags taken up from outside can be presented by class I MHC

Question 30

Ags recognized by B cells can be in soluble or cell surface associated form. Activated B cell is transformed into a _________ cell that secretes Abs. There are primarily found where?

Answer 30

Plasma cell -> primarily found in lymphoid organs

Question 31

Ig___ and Ig___ are associated with BCR

Answer 31

Igalpha and Igbeta

Question 32

Surface Ig can be of what 2 classes?

Answer 32

IgM and IgD

Question 33

Ig___ is the major Ag receptor isotype coexpressed with IgM on the surface of most peripheral B cells in humans

Answer 33

IgD

Question 34

How are the alpha and beta chains of the TCR complex linked?

Answer 34

Disulphide linked

Question 35

What are the 3 invarient domains associated with the TCR complex?

Answer 35

Epsilon/delta(CD3), Gamma/epsilon (CD3), zeta/zeta

Question 36

CD___ is an identification marker for all T cells

Answer 36

CD3

Question 37

_________ APC that expresses class II MHC but not co-stimulatory molecules cannot activate T cells

Answer 37

Resting

Question 38

__________ APC expresses high level of MHC and co-stimulatory molecules

Answer 38

Activated

Question 39

Gamma/delta T cells are a major T cell population in ____________ tissues

Answer 39

Epithelial

Question 40

What type of T cells are directly activated by PRRs (without APCs)?

Answer 40

Gamma/delta T cells

Question 41

What type of T cell is believed to have a prominent role in recognition of lipid Ags?

Answer 41

Gamma/delta T cells

Question 42

Do gamma/delta T cells have memory?

Answer 42

No!

Question 43

Natural killer cells assess whether other cells are abnormal by detecting types and levels of surface-associated A) MHC class I molecules B) Nonself molecules C) Pathogen-associated molecular patterns D) Pattern recognition receptors E) Somatically generated cell surface receptors

Answer 43

A) MHC class I molecules

Question 44

What is the most abundant Ig isotype in the blood?

Answer 44

IgG

Question 45

What is a proteolytic fragment of an Ab molecule that contains one intact Ag-binding site called?

Answer 45

Fab

Question 46

T/F: The principal form of cell-mediated immunity that protects against viral infections is mediated by CD8+ CTLs

Answer 46

True

Question 47

T/F: cell-mediated immunity can be adoptively transferred by injecting serum from one individual to another

Answer 47

False

Question 48

The induction phase of a cell-mediated immune response includes which of the following events? A) CD4+ T cell secretion of IFN-gamma leading to macrophage activation B) CD8+ T cell lysis of a virally infected cell C) Clonal expansion of CD8+ T cells with a LN D) Migration of CD4+ effector T cells from blood vessels into a tissue site of infection E) Migration of a naive CD4+ T cell from the thymic medulla into the circulation

Answer 48

C) Clonal expansion of CD8+ T cells with a LN

Question 49

Which of the following is a function of TNF that is important in the defense against infections and is likely to be impaired in the setting of TNF blockade? A) Induction of fever B) Reduction in cardiac output C) Enhanced procoagulant activity of endothelial cells D) Enhanced glucose utilization by muscle cells E) Induction of E-selectin expression on endothelial cells

Answer 49

E) Induction of E-selectin expression on endothelial cells

Question 50

What is the proteolytic fragment of an Ab molecule that contains the heavy chain constant region called?

Answer 50

Fc

Question 51

``` Differentiation of Th2 cells from naive precursor cells is dependent on which of the following? A) TLR ligands B) Presence of IL-12 C) Absence of IL-12 D) NF-kB E) Interferon-alpha ```

Answer 51

C) Absence of IL-12

Question 52

Which of the following mechanisms does not contribute to the generation of a CTL response to a viral infection? A) DCs phagocytose infected cells or viral particles and present them to naive CD8+ T cells via the class I MHC pathway B) DCs are infected with the virus and present viral peptides to naive CD8+ T cells via the class I MHC pathway C) CTLs are directly activated by CD40L expressed on activate Th cells through CD40 D) Th cells secrete IL-2 that promotes proliferation and differentiation of CD8+ T cells E) Th cells activate APCs via the CD40L-CD40 pathway, and the activated APCs present viral peptides to naive CD8+ T cells via the class I MHC pathway

Answer 52

C) CTLs are directly activated by CD40L expressed on activated Th cells through CD40

Question 53

``` Which of the following anatomic regions is normally protected from pathogens only by humoral immune responses and not by cell-mediated immune responses? A) skin B) intestinal lumen C) intestinal epithelium D) CNS E) spleen ```

Answer 53

B) intestinal lumen

Question 54

Up to half of the IgG found in the serum of a normal individual is produced by what cells?

Answer 54

Long-lived plasma cells in the bone marrow

Question 55

``` Treatment of Abs with the enzymes papain under conditions of limited proteolysis results in hinge-region cleavage, yielding monovalent Ag-binding Fab fragments that lack a constant region. Which effector function of Abs would Fab fragments be able to perform? A) Complement pathway activation B) ADCC C) Opsonization D) Ag cross-linking and precipitation E) Microbe neutralization ```

Answer 55

E) Microbe neutralization

Question 56

Activation of the Th1 response requires which of the following? A) Cross-linking of B cell receptors B) Binding of CD8 to MHC class I C) Presence of IL-12 secreted by macrophages D) IL-2 and IFN-gamma E) Class switching of IgM to IgE

Answer 56

C) Presence of IL-12 secreted by macrophages

Question 57

IgE is important in defense against parasites because A) It crosslinks mast cell FcepsilonRI, causing degranulation of inflammatory granules B) It causes neutrophil chemotaxis C) It increases production of IL-1 and IFN-gamma D) It is an indicator of memory B cell function E) It binds to surface Ags on parasites and causes opsonization

Answer 57

A) It crosslinks mast cell FcepsilonRI, causing degranulation of inflammatory granules