Helper T Cells and Their Response to Antigen

Question 1

What are the four major populations of lymphocytes with antigen-binding receptors and their roles?

Answer 1

Helper T cells - regulate immune responses

Effector or cytotoxic T cells - destroy cells expressing endogenous antigens

Regulatory T cells - control everything

B cells - produce antibodies

Question 2

Exogenous antigen is trapped and processed by _________ and other ______________ and then presented to ____________.

Answer 2

Exogenous antigen is trapped and processed by dendritic and other antigen-presenting cells and then presented to helper T cells.

Question 3

If a helper T-cell receptor binds an antigen in the correct manner, the helper T cell is activated and initiates an immune response by ___________, _________, and _____________

Answer 3

If a helper T-cell receptor binds an antigen in the correct manner, the helper T cell is activated and initiates an immune response by secreting cytokines, dividing, and differentiating

Question 4

Other antigen-responsive cell populations, the ________ and the ______________, cannot respond to antigens unless they are stimulated by helper T cells.

Answer 4

Other antigen-responsive cell populations, the B cells and the cytotoxic T cells, cannot respond to antigens unless they are stimulated by helper T cells.

Question 5

Important proteins with multiple domains include the ____________________, the ____________________, and the _______________________.

Answer 5

Important proteins with multiple domains include the B cell antigen receptors (BCRs), the T cell antigen receptors (TCRs), and the MHC class I and II molecules.

Question 6

The four key antigen receptors of the immune system are each constructed using ______________ as building blocks. Each binds antigen through the use of ___________. All are members of the __________________.

Answer 6

The four key antigen receptors of the immune system are each constructed using immunoglobulin domains as building blocks. Each binds antigen through the use of variable domains. All are members of the immunoglobulin superfamily.

Question 7

The N-terminal of the TCR is called the…

Answer 7

variable domain

Question 8

The C-terminal domain within the cytoplasm of the T cell is called the….

Answer 8

transmembrane domain

Question 9

The paired chains are joined by a ____________ between their _____________________ to form a stable heterodimer.

Answer 9

The paired chains are joined by a disulfide bond between their constant domains to form a stable heterodimer.

Question 10

What is the hypervariable or the complementary determining region (CDR)?

Answer 10

region with highly variable amino acid sequence

comes into contact with the antigen

Question 11

The two antigen-binding chains of each TCR are associated with a cluster of signal transducing proteins called the

Answer 11

CD3 complex

Question 12

The TCR β chain is linked to the _______ dimer, and the TCR α chain is linked to the ________ dimer

Answer 12

β chain - γ-ε (gamma, epsilon)

α chain - δ-ε (delta, epsilon)

Question 13

About 80% of α/β TCRs use ____ dimers. The remaining 20% use _____ heterodimers.

Answer 13

About 80% of α/β TCRs use ζζ (zeta, zeta) dimers. The remaining 20% use ηζ (eta, zeta) heterodimers.

Question 14

CD4, found only on ____________, binds ____________ molecules on _______________ cells.

Answer 14

CD4, found only on helper T cells, binds MHC class II molecules on antigen presenting cells.

Question 15

CD8 is found only on ___________ and binds ___________ molecules on ______________ or ______________.

Answer 15

CD8 is found only on cytotoxic T cells and binds MHC class I molecules on virus-infected or abnormal cells.

Question 16

______ and ______ enhance TCR signal transduction 100-fold when they cross-link to an MHC molecule on an antigen-presenting cell

Answer 16

CD4 and CD8 enhance TCR signal transduction 100-fold when they cross-link to an MHC molecule on an antigen-presenting cell

Question 17

What is a ligand

Answer 17

a signal-triggering molecule binding to a site on a target protein

Question 18

Induction of Th17 cells occurs by exposure to a cytokine mixture containing ________ and _________. Differentiation is promoted by _________ and maintained by _______. Th17 cells promote ___________.

Answer 18

Induction of Th17 cells occurs by exposure to a cytokine mixture containing TGF-β and IL-6. Differentiation is promoted by IL-21 and maintained by IL-23. Th17 cells promote inflammation.

Question 19

Unlike conventional antigens that must bind within the grooves of both an MHC molecule and a TCR, ____________ directly link a TCR V_βdomain to an MHC class II molecule on the antigen-presenting cell.

Answer 19

superantigens

Question 20

Superantigens (SAgs) are a class of antigens that cause ___________ activation of T-cells resulting in polyclonal T cell activation and massive ____________. SAgs are produced by some ____________ and _____________.

Answer 20

Superantigens (SAgs) are a class of antigens that cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release. SAgs are produced by some viruses and bacteria.

Question 21

The differentiation of ______ cells is driven by IL-12 produced by antigen-presenting _____________ cells (DC1), macrophages (M1), and B cells plus co-stimulation by CD80.

Answer 21

The differentiation of Th1 cells is driven by IL-12 produced by antigen-presenting myeloid dendritic cells (DC1), macrophages (M1), and B cells plus co-stimulation by CD80.

Question 22

Th1 cells promote _____________ immune responses such as the delayed hypersensitivity reaction and macrophage activation. They thus generate immunity to ___________ organisms such as mycobacteria and to viruses

Answer 22

Th1 cells promote cell-mediated immune responses such as the delayed hypersensitivity reaction and macrophage activation. They thus generate immunity to intracellular organisms such as mycobacteria and to viruses

Question 23

Dendritic cells that do not secrete IL-12 promote __________ cell differentiation

Answer 23

Th2

Question 24

Th2 cells respond optimally to antigen presented by_____________________ (______ cells) and macrophages, and less well to antigen presented by B cells

Answer 24

Th2 cells respond optimally to antigen presented by plasmacytoid dendritic cells (DC2 cells) and macrophages, and less well to antigen presented by B cells

Question 25

The cytokines from Th2 cells enhance B cell production of _____ and ______ up to 20-fold and production of ______ up to 1000-fold.

Th2 responses are associated with enhanced immunity to ____________ but with decreased resistance to mycobacteria and other intracellular organisms.

Answer 25

The cytokines from Th2 cells enhance B cell production of IgG and IgA up to 20-fold and production of IgE up to 1000-fold.

Th2 responses are associated with enhanced immunity to parasitic worms but with decreased resistance to mycobacteria and other intracellular organisms.

Question 26

Different antigens can trigger distinctly different Th cell subpopulations. For example, T cells exposed to a parasite antigen from the roundworm Toxocara canismount a _______ response and secrete primarily ______ and _______. In contrast, T cells exposed to PPD, an antigen from Mycobacterium tuberculosis, mount a ______ response characterized by secretion of ______ and _______.

Answer 26

Different antigens can trigger distinctly different Th cell subpopulations. For example, T cells exposed to a parasite antigen from the roundworm Toxocara canis mount a Th2 response and secrete primarily IL-4 and IL-5. In contrast, T cells exposed to PPD, an antigen from Mycobacterium tuberculosis, mount a Th1 response characterized by secretion of IFN-γ and IL-2.

Question 27

Of the cytokine mixture that promotes Th17 differentiation, ________ appears to be of greatest importance since it enhances IL-17 expression.

Answer 27

IL-23

Question 28

True or False,

The variable domain of the TCR is explicit for binding a specific antigen.

Answer 28

True

Question 29

True or False,

TCR, BCR, MHC I, and MHCII are not members of the Immunoglobulin superfamily.

Answer 29

False

Question 30

If a processed and presented antigen binds in a correct manner on a T cell, the T cell is activated and initiates the immune response by:

A. Cytokine production

B. Mitosis

C. Cell differentiation

D. All of the above

Answer 30

D. All of the above

Question 31

True or False

CD3 is found in all T cells and has a main role in the signal transduction into the T cell.

Answer 31

True

Question 32

Important surface antigens of T cells

Answer 32

CD2

CD3

CD4

CD8

Question 33

H3 is a receptor for…

Answer 33

histamine

Question 34

Receptor for IL-2

Answer 34

CD25

Question 35

Receptor for CD58 (originating from Antigen presenting cells)

Answer 35

CD2

Question 36

Receptor for complement

Answer 36

CD35 (C3b, C4b)

Question 37

Receptor for immunoglobulins

Answer 37

FcR

Question 38

Transport receptor for transferrin

Answer 38

CD71

Question 39

What are the corresponding receptors for the immunoglobulins IgM, IgG and IgE

Answer 39

IgM - FcµR

IgG - CD32

IgE - CD23

Question 40

CD25 is the α chain of the _______ receptor. CD25 associates with the ß chain _________.

Answer 40

CD25 is the α chain of the IL-2 receptor. CD25 associates with the ß chain CD122.

Question 41

CD124 is the _______ receptor expressed on T and B cells, fibroblasts, endothelial cells, and stem cells.

Answer 41

CD124 is the IL-4 receptor expressed on T and B cells, fibroblasts, endothelial cells, and stem cells.

Question 42

CD125 is the ________ receptor α chain

Answer 42

CD125 is the IL-5 receptor α chain