Chapter 5: 5-1 through 5-16

Question 1

The sole function of B cells is to make antibodies whereas T-cells…

Answer 1

have more diverse roles, all of which involve interactions with other cells.

Question 2

What is the main difference between B cells and T cells?

Answer 2

The type of antigen they recognize.

Question 3

What is a TCR?

Answer 3

T-cell receptor that is the antigen receptor on a T-cell

Question 4

What do TCR’s and immunoglobins have in common?

Answer 4

similar structure
produced as a result of gene rearrangement
highly variable and diverse in their antigen specificity
expresses a single species of antigen receptor

Question 5

How are B cells and T cells different when it comes to the antigens they recognize?

Answer 5

Immunoglobulins bind epitopes on a wide range of intact molecules, such as proteins, carbohydrates, and lipids. These kinds of epitope are present on the surfaces of bacteria, viruses, and parasites, and also on soluble protein toxins.
T-cell receptors, in contrast, recognize and bind mainly to peptide antigens, which are derived from the pathogen’s proteins.

Question 6

What is the ligand for a T cell receptor made of?

Answer 6

A combination of a peptide antigen and MHC molecule on a cell surface.

Question 7

Genes that encode the MHC molecules are clustered in a chromosomal region called the…

Answer 7

Major histocompatibility complex (MHC)

Question 8

Some of the genes for MHC proteins are highly polymorphic, thus there are numerous different variants of these genes in the human population. T/F

Answer 8

True, these differences in MHC are the major cause of tissue incompatibility and transplant rejection.

Question 9

What is the T-cell receptor?

Answer 9

A membrane-bound glycoprotein (resembles a single antigen-binding arm of an immunoglobulin molecule).
Has two different polypeptide chains and has one antigen-binding site.

Question 10

Does a T-cell receptor differentiate with the equivalent of somatic hypermutation of the binding site or switching of the constant-region of the isotype as occurs for Immunoglobulins?

Answer 10

No, because once the T cell is stimulated with an antigen there is no further change in the T-cell receptors.

Question 11

T-cell receptors can serve as a antigen receptor and effector molecule. T/F

Answer 11

False. B cells can serve as an antigen receptor and effector molecule. T cells can only serve as an antigen receptors.

Question 12

What contributes to the fact that theyre are millions of different T cell receptors?

Answer 12

The genes that encode for the alpha and beta chains of the receptor have germline organization similar to that of the immunoglobulin heavy-chain and light-chain genes, comprising sets of gene segments that must be rearranged to form a functional gene. As a consequence of the gene rearrangements that occur during T-cell development, each mature T cell expresses one functional alpha chain and one functional beta chain, which together define a unique T-cell receptor molecule.

Question 13

Where are the CDR loops located in a T cell receptor and how many are there?

Answer 13

There are three CDR loops each in the V domains of the alpha chain and the beta chain.

Question 14

Immunoglobulins possess two or more binding sites for an antigen but a T-cell receptor possesses…

Answer 14

a single binding site for antigen and are used only as cell-surface receptors for antigen, never as soluble antigen-binding molecules. , thus achieving multipoint attachment.

Question 15

Multipoint attachment occurs between T cell receptors and another cell surface by?

Answer 15

Antigen binding to T cell receptors occurs always in the context of two opposing cell surfaces, where multiple copies of the T-cell receptor bind to multiple copies of the antigen: MHC complex on the opposing cell.

Question 16

What two categories of mechanisms generate immunoglobulin diversity?

Answer 16

Those operating before the B cell is stimulated with specific antigen.
Those operating afterward.

Question 17

What mechanism(s) is used to generate diversity in B cells by operating BEFORE the B cell is stimulated by a specific antigen?

Answer 17

Gene rearrangements that generate the V-region sequence.

Question 18

What mechanism(s) is used to generate diversity in B cells by operating AFTER the B cell is stimulated by a specific antigen?

Answer 18

Changes in mRNA splicing that produce a secreted immunoglobulin, C-region DNA rearrangements that switch the heavy-chain isotype, and somatic hypermutation of the V-region gene to produce antibodies of higher affinity.

Question 19

In T cells the mechanisms that generate diversity before antigen stimulation are essentially the same as those in B cells, but after antigen stimulation B cells continues to diversify, the genes encoding T-cell receptors remain unchanged. T/F

Answer 19

True, this fundamental difference reflects the use of the T-cell receptor only for the recognition of antigen and not for mediating effector functions, which are handled by other proteins produced by T cells.

Question 20

The human T-cell locus for the alpha chain and beta chain are where?

Answer 20

Alpha chain locus - chromosome 14

Beta chain locus - chromosome 7

Question 21

The T-cell receptor alpha chain locus is otherwise similar to an immunoglobulin _____-chain locus, containing only sets of __ and __ gene segments; the beta chain locus is similar to an immunoglobulin ____-chain locus, containing __ segments in addition to ___ and __ segments.

Answer 21

The T-cell receptor alpha chain locus is otherwise similar to an immunoglobulin light-chain locus, containing only sets of V and J gene segments; the beta chain locus is similar to an immunoglobulin heavy-chain locus, containing D segments in addition to V and J segments.

Question 22

T-cell receptor gene rearrangement occurs during T-cell development in the…

Answer 22

thymus

Question 23

How does gene rearrangement occur in T-cells?

Answer 23

In the alpha chain gene, a V gene segment is jointed to a J gene segment by somatic DNA recombination to make the V-region sequence.
In the beta chain gene, recombination first joins a D and a J gene segment, which are then joined to a V gene segment.
The T-cell receptor gene segments are flanked by recombination signal sequences similar to those found in the immunoglobulin genes, and the RAG complex and the same DNA-modifying enzymes are involved in the recombination process. During recombination, additional, nontemplated P and N nucleotides are inserted in the junctions between the V and J gene segments of the alpha chain sequence. These mechanisms contribute junctional diversity in the CDR3 to T-cell receptor alpha and beta chains.

Question 24

What is the cause of a rare syndrome called severe combined immunodeficiency disease (SCID)?

Answer 24

genetic defects that result in the absence of RAG proteins. The disease is called “combined” because functional B and T lymphocytes are both absent, and it is “severe” compared with immunodeficiency in which only B cells are lacking.

Question 25

Rare cases of missense mutations that produce RAGE proteins with partial enzymatic activity cause a rapidly fatal immunodeficiency is known as…

Answer 25

Omenn syndrome

Question 26

After gene rearrangement, functional alpha and beta chain genes consist of exons that encode the…

Answer 26

leader peptide, the V region, the C region, and the membrane-spanning region.

Question 27

When the gene is transcribed, the primary RNA transcript is spliced to remove the introns and is processed to give?

Answer 27

mRNA which is then translated to produce alpha and beta chains. Newly synthesized alpha and beta chains enter the endoplasmic reticulum where they pair to form the alpha beta T-cell receptor.

Question 28

5-1 In which of the following ways are T-cell receptors distinct from immunoglobulins? Select all that apply
A. T-cell receptors are generated through somatic recombination.
B. The T-cell repertoire encompasses a very large degree of diversity.
C. T-cell receptors are never secreted subsequent to antigen encounter.
D. The variable region of T-cell receptors contains complementarity-determining regions that interact with antigen.
E. T-cell receptors are used solely for the purpose of antigen recognition and not for effector function.

Answer 28

C. T-cell receptors are never secreted subsequent to antigen encounter.
E. T-cell receptors are used solely for the purpose of antigen recognition and not for effector function.

Question 29

1. Regions exhibiting the highest amount of diversity between T-cell receptors.
   A. four extracellular domains
   B. T-cell receptor complex
   C. Complementarity-determining regions (CDRs)
   D. Valpha and Vbeta domains
   E. gama:delta T-cell receptor

Answer 29

D. Valpha and Vbeta domains

Question 30

2.  Resembles a Fab fragment of IgG
A.  four extracellular domains
B.  T-cell receptor complex
C.  Complementarity-determining regions (CDRs)
D.  Valpha and Vbeta domains
E.  gama:delta T-cell receptor

Answer 30

A. four extracellular domains

Question 31

3. T-cell receptor, CD3 complex plus zeta chains
   A. four extracellular domains
   B. T-cell receptor complex
   C. Complementarity-determining regions (CDRs)
   D. Valpha and Vbeta domains
   E. gama:delta T-cell receptor

Answer 31

B. T-cell receptor complex

Question 32

4. Found on small subset of T-cell population
   A. four extracellular domains
   B. T-cell receptor complex
   C. Complementarity-determining regions (CDRs)
   D. Valpha and Vbeta domains
   E. gama:delta T-cell receptor

Answer 32

E. gama:delta T-cell receptor

Question 33

5. membrane-distal loops forming antigen-binding sites
   A. four extracellular domains
   B. T-cell receptor complex
   C. Complementarity-determining regions (CDRs)
   D. Valpha and Vbeta domains
   E. gama:delta T-cell receptor

Answer 33

C. Complementarity-determining regions (CDRs)

Question 34

5-3 All of the following have been observed in individuals deficient in either CD3delta or CD3epsilon except
A. their T-cell receptors fail to signal effectively
B. there is an increase in the number of gama:delta T cells in the circulation
C. their T-cell receptors are not transported effectively to the cell surface
D. their T cells express a lower number of T-cell receptors on the cell surface
E. they are immunodeficient

Answer 34

B. there is an increase in the number of gama:delta T cells in the circulation

Question 35

5-4 A primary difference between how B cells recognize antigen and how T cells recognize antigen is that
A. T-cell receptors can bind antigen only after secretion of the T-cell receptor from the surface of the T cell
B. antibodies can bind only to denatured proteins
C. T-cell receptors can bind to carbohydrate groups or clusters of amino acids
D. B cells recognize degraded proteins bound to major histocompatibility molecules
E. T cells recognize degraded proteins bound to major histocompatibility molecules

Answer 35

E. T cells recognize degraded proteins bound to major histocompatibility molecules

Question 36

5-5 Which of the following statements regarding CD4 is incorrect?
A. MHC class II molecules present antigens to CD4 T cells.
B. CD4 is the receptor used for HIV entry into CD4 T cells.
C. CD4 is made up of two separate membrane-bound chains.
D. Late in the progression of an HIV infection, the number of CD4 T cells in the circulation diminishes.
E. CD4 is referred to as a T-cell co-receptor.

Answer 36

C. CD4 is made up of two separate membrane-bound chains.

Question 37

1.  presentation of extracellular sources of antigen by class I MHC molecules
A.  Invariant chain
B.  Cross-presentation
C.  MHC class I
D.  MHC class II
E. betat2-microglobulin

Answer 37

B. Cross-presentation

Question 38

2.  Present peptides to CD8 T cells
A.  Invariant chain
B.  Cross-presentation
C.  MHC class I
D.  MHC class II
E. betat2-microglobulin

Answer 38

C. MHC class I

Question 39

3.  One of the soluble MHC-associated chains that is highly conserved.
A.  Invariant chain
B.  Cross-presentation
C.  MHC class I
D.  MHC class II
E. betat2-microglobulin

Answer 39

E. betat2-microglobulin

Question 40

4.  Transports MHC molecules to endocytic vesicles
A.  Invariant chain
B.  Cross-presentation
C.  MHC class I
D.  MHC class II
E. betat2-microglobulin

Answer 40

A. Invariant chain

Question 41

5.  Present peptides to CD4 T cells
A.  Invariant chain
B.  Cross-presentation
C.  MHC class I
D.  MHC class II
E. betat2-microglobulin

Answer 41

D. MHC class II

Question 42

5-7 In regard to antigen presentation, MHC class I molecules usually present peptides derived from ______, whereas MHC class II molecules usually present peptides derived from ________.
A. Intracellular cytostolic sources; vesicular system
B. Phagolysosome; proteasomes
C. MIIC; self proteins
D. CLIP; HLA-DM
E. endocytic vesicles; endoplasmic reticulum.

Answer 42

A. Intracellular cytostolic sources; vesicular system

Question 43

Match the molecule or domain of molecules to what it binds. (1) MHC class I-associated peptide
A. a1 and b1 domains
B. b2-microglobulin
C. CLIP
D. b2 domain of MHC class II
E. a1 and a2 domains of MHC class I molecules
F. a3 domain of MHC class I molecules

Answer 43

E. a1 and a2 domains of MHC class I molecules

Question 44

Match the molecule or domain of molecules to what it binds. (2) CD4
A. a1 and b1 domains
B. b2-microglobulin
C. CLIP
D. b2 domain of MHC class II
E. a1 and a2 domains of MHC class I molecules
F. a3 domain of MHC class I molecules

Answer 44

D. b2 domain of MHC class II

Question 45

Match the molecule or domain of molecules to what it binds. (3) MHC class II molecules in MIIC
A. a1 and b1 domains
B. b2-microglobulin
C. CLIP
D. b2 domain of MHC class II
E. a1 and a2 domains of MHC class I molecules
F. a3 domain of MHC class I molecules

Answer 45

C. CLIP

Question 46

Match the molecule or domain of molecules to what it binds. (4) MHC class I-a chain
A. a1 and b1 domains
B. b2-microglobulin
C. CLIP
D. b2 domain of MHC class II
E. a1 and a2 domains of MHC class I molecules
F. a3 domain of MHC class I molecules

Answer 46

B. b2-microglobulin

Question 47

Match the molecule or domain of molecules to what it binds. (5) MHC class II-associated peptide
A. a1 and b1 domains
B. b2-microglobulin
C. CLIP
D. b2 domain of MHC class II
E. a1 and a2 domains of MHC class I molecules
F. a3 domain of MHC class I molecules

Answer 47

A. a1 and b1 domains

Question 48

Match the molecule or domain of molecules to what it binds. (6) CD8
A. a1 and b1 domains
B. b2-microglobulin
C. CLIP
D. b2 domain of MHC class II
E. a1 and a2 domains of MHC class I molecules
F. a3 domain of MHC class I molecules

Answer 48

F. a3 domain of MHC class I molecules

Question 49

5-9 Identify which of the following statements regarding peptide-MHC molecule interactions are correct. (Select all that apply)
A. Peptides with different amino acid sequences may be able to bind to the same type of MHC molecule
B. Covalent bonds hold the peptide in the groove of the MHC molecule
C. The length of peptides bound by MHC class I molecules is shorter than that of those bound by MHC class II molecules
D. The groove of the MHC molecule is deep enough to accommodate two or more peptides
E. Binding pockets of MHC molecules anchor the side chains of only certain amino acids of the peptide.
F. The amino- and carboxy-terminal amino acids of peptides are used for binding to MHC class I molecules, whereas amino acids along the length of the peptide are used for biding to MHC class II molecules.
G. Only non-self peptides form stable interactions with MHC molecules
H. The type of MHC molecule presenting a non-self protein is informative regarding whether the pathogen originated from an intercellular or extracellular source.

Answer 49

A.  Peptides with different amino acid sequences may be able to bind to the same type of MHC molecule
C.  The length of peptides bound by MHC class I molecules is shorter than that of those bound by MHC class II molecules
E.  Binding pockets of MHC molecules anchor the side chains of only certain amino acids of the peptide.
F.  The amino- and carboxy-terminal amino acids of peptides are used for binding to MHC class I molecules, whereas amino acids along the length of the peptide are used for biding to MHC class II molecules.
H.  The type of MHC molecule presenting a non-self protein is informative regarding whether the pathogen originated from an intercellular or extracellular source.

Question 50

5-10  MHC class I molecules present peptide antigens derived from a(n) \_\_\_\_\_\_\_\_\_ compartment, whereas MHC class II molecules present peptide antigens derived from a(n) \_\_\_\_\_\_\_\_ compartment:
A.  extracellular; intracellular
B.  intracellular: extracellular
C.  opsonization; neutralization
D.  neutralization; opsonization
E.  none of the above

Answer 50

B. intracellular: extracellular

Question 51

5-11 Amino acid variation among MHC class II allotypes that present antigens to CD4 T cells is concentrated
A. where MHC contacts the co-receptors CD4 or CD8
B. in the beta chain, because the alpha chain is monomorphic
C. where the MHC molecule contacts peptide and the T-cell receptor
D. in the alpha chain, because the beta chain is monomorphic
E. throughout both the alpha and beta chains in all domains

Answer 51

C. where the MHC molecule contacts peptide and the T-cell receptor

Question 52

5-12  The T-cell co-receptor CD4 interacts with \_\_\_\_\_ bound to the surface of \_\_\_\_\_.
A.  MHC class I; antigen-presenting cells
B.  MHC class I; T cells
C.  MHC class II; antigen-presenting cells
D.  MHC class II; T cells
E.  none of the above

Answer 52

C. MHC class II; antigen-presenting cells

Question 53

5-13  The high degree of polymorphism in MHC class I molecules tha tpresent antigens to CD8 T cells is found in \_\_\_\_\_\_\_ because \_\_\_\_\_\_ is/are monomorphic.
A.  B2-microglobulin; the heavy chain
B.  both the a and b chains; none
C.  HLA-DOB; HLA-DOA
D.  the heavy chain; B2-microglobulin
E.  HLA-E and HLA-G; HLA-F

Answer 53

D. the heavy chain; B2-microglobulin

Question 54

At 5 months of age, Christina Kitchenman was admitted to the hospital with a fever and a sever cough that was caused by an opportunistic yeast-like fungus.  Her CD4 T-cell count was much lower than expected.  Her B-cell count was slightly higher than normal.  Christina's T cells did not respond to a specific antigen stimulus even though she had the vaccination previously.  Normal T-cell proliferation responses, however, were detected upon exposure of peripheral blood mononuclear cells to allogeneic B lymphocytes.  Further tests revealed hypogammaglobulinemia, a deficiency of all MHC class II isotypes on her white blood cells, but no deficiency of MHC class I isotypes.  A genetic defect in which of the following would support this diagnosis?
A.  HLA-DQ
B.  CIITA (MHC class II transactivator)
C.  RAG-1
D.  TAP-1
E.  CD3e

Answer 54

The correct answer is B. CIITA is the major transcriptional control factor for MHC class II gene expression. In the absence of functional CIITA, the expression of all MHC class II genes and the invariant-chain gene is compromised. This in turn negatively affects the intrathymic development and functionality of CD4 T cells, accounting not only for the severely reduced levels of CD4 T cells but also for the hypogammaglobulinemia observed in Christina. A mutation in HLA-DQ would not explain the failure to detect other MHC class II isotypes. The existence of both B and T cells rules out a RAG-1 defect, which would result in the inability to rearrange both immunoglobulin and T-cell receptor genes. TAP-1 is not associated with MHC class II expression but instead influences MHC class I expression. Finally, a defect in CD3e would result in impairment of all T-cell responses, but this was not observed in the in vitro functionality tests involving allogeneic B cells.

Question 55

Brittany Hudson, was seen by her physician after the development of a small pustule around her nostrils. Flow-cytometric analysis of peripheral blood revealed abnormally low numbers of MHC class I molecules on cell surfaces and abnormally low numbers of CD8 T cells. A diagnosis of type I bare lymphocyte syndrome was made. A deficiency in which of the following would explain this etiology?
A. HLA-DM
B. invariant chain
C. class II-associated invariant chain peptide (CLIP)
D. TAP-1 or TAP-2
E. MHC class II transactivator (CIITA)

Answer 55

The correct answer is d. A deficiency in either TAP-1 or TAP-2, which function to transport peptide fragments to the lumen of the endoplasmic reticulum, would inhibit the expression of MHC class I on the cell surface because peptide must be bound to an MHC class I molecule to permit its transport from the endoplasmic reticulum to the cell membrane. Low levels of MHC class I account for the low levels of CD8 T cells; MHC class I-restricted CD8 T cells would fail to undergo positive selection in the thymus if MHC class I levels were abnormally low. Deficiencies of HLA-DM, invariant chain ( which gives rise to CLIP), or CIITA would affect the MHC call I pathway.

Question 56

1. Which of the following statements regarding T-cell receptor recognition of antigen is correct?
   A. T-cell receptors recognize antigen only as a peptide bound to an MHC molecule
   B. T-cell receptors recognize antigens in their native form
   C. T-cell receptors, like B-cell immunoglobulins can recognize carbohydrate, lipid, and protein antigens
   D. Antigen processing occurs in extracellular spaces

Answer 56

A. T-cell receptors recognize antigen only as a peptide bound to an MHC molecule

Question 57

2. MHC class I molecules present peptide antigens derived from a(n) \_\_\_\_\_\_\_ compartment, whereas MHC class II molecules present peptide antigens derived from a(n) \_\_\_\_\_\_\_ compartment: 
A. extracellular:: intracellular 
B. intracellular::extracellular 
C. opsonization::neutralization 
D. neutralization::opsonization

Answer 57

B. intracellular::extracellular

Question 58

3. Which of the following describes the sequence of events involved in processing of peptides that will be presented as antigen with MHC class I?
   A. TAP –> proteasome –> MHC I –> ER –> plasma membrane
   B. plasma membrane –> proteasome –> MHC I –> ER –> plasma membrane
   C. proteasome –> TAP –> MHC I –> ER –> plasma membrane
   D. proteasome –> TAP –> ER –> MHC I –> plasma membrane
   E. ER –> proteasome –> MHC I –> TAP –> plasma membrane

Answer 58

D. proteasome –> TAP –> ER –> MHC I –> plasma membrane

Question 59

4. Which of the following characteristics is common to both T-cell receptors and immunoglobulins?
   A. Somatic recombination of V, D and J segments is responsible for the diversity of antigen-binding sites.
   B. Somatic hypermutation changes the affinity of antigen-binding sites and contributes to further diversification.
   C. Class switching enables a change in effector function.
   D. The antigen receptor is composed of two identical heavy chains and two identical light chains.

Answer 59

A. Somatic recombination of V, D and J segments is responsible for the diversity of antigen-binding sites.

Question 60

5. Which of the immunoglobulin isotypes would be most important for neutralizing polio virus before it could infect intestinal cells? 
A. Correct secretory IgA 
B. serum IgA 
C. serum IgD 
D. secretory IgG 
E. Membrane IgM

Answer 60

A. Correct secretory IgA

Question 61

6. What are the regions of the antibody contributes MOST to the affinity of the antibody for antigen? 
A. Correct CDR 
B. Fab 
C. Fc 
D. hinge region 
E. loops in the Fc region

Answer 61

A. Correct CDR

Question 62

7. What factor or structural element of a antibody determines its isotype form?
   A. antigen specificity
   B. Heavy chain constant region
   C. Light chain constant region
   D. number of antigen binding sites
   E. number of Variable and constant domains

Answer 62

B. Correct Heavy chain constant region

Question 63

8. The _______ contribute to antigen specificity of immunoglobulins, and _______ make up the more conservative flanking regions:
   A. hypervariable loops; framework regions
   B. constant domains; variable domains
   C. heavy chains; light chains
   D. variable gene segments; joining gene segments

Answer 63

A. hypervariable loops; framework regions

Question 64

The derivation of antibodies from a single clone of B lymphocytes that have identical antigen specificity.

Answer 64

Monoclonal antibody production

Question 65

Change of immunoglobulin class but preservation of antigen specificity.

Answer 65

isotype switching

Question 66

Nucleotide changes in variable regions of immunoglobulin genes affecting affinity for antigen.

Answer 66

somatic hypermutation

Question 67

Enhancement of receptor-mediated phagocytosis of immunoglobulin-coated antigen.

Answer 67

opsonization

Question 68

The rearrangement of V, D, and J segments to form an immunoglobulin.

Answer 68

somatic recombination

Question 69

10. Which immunoglobulin’s main function is to mediate sensitization of mast cells? 
A. IgA 
B. IgD 
C. IgE 
D. IgG 
E. IgM

Answer 69

C. IgE