Chapter 4 Flashcards
Which of the following statements regarding immunoglobulin light chains is correct?
a. Kappa light chain associates with only particular heavy-chain isotypes.
b. There is no functional difference between kappa and lambda.
c. A given antibody may contain just kappa, or just lambda, or both.
d. Most antibodies in humans contain kappa light chains.
e. Light chains possess only framework regions, not hypervariable regions
There is no functional difference between kappa and lambda.
An epitope is the specific part of the antigen that is recognized by an antibody and binds to the complementarity-determining regions in the antibody variable domains. Epitopes are sometimes referred to as antigenic determinants. Epitopes can be part of a protein or can be carbohydrate or lipid structures present in the glycoproteins, polysaccharides, glycolipids, and proteoglycans of pathogens.
True
Indicate which of the following statements is false
a. Light chains contain V and J segments, whereas heavy chains contain V, D, and J segments.
b. The Vk gene segments are duplicated in about 50% of the human population.
c. All immunoglobulin loci include a leader sequence.
d. On the heavy-chain locus, V rearranges to D first, and then J joins the combined VD sequence.
e. Immunoglobulin heavy-chain loci undergo two rounds of somatic recombination, whereas light-chain loci undergo only one.
On the heavy-chain locus, V rearranges to D first, and then J joins the combined VD sequence.
The five isotypes of immunoglobulin differ from each other in their _____.
a. light-chain constant regions
b. heavy-chain constant regions
c. light-chain variable regions
d. heavy-chain variable regions
e. heavy-chain variable and constant regions
heavy-chain constant regions
Gene rearrangement by somatic recombination involves recombination signal sequences (RSSs) that flank V, D, and J segments and are recognized by the enzymes involved in cutting and rejoining the gene segments. An RSS is composed of a conserved nonamer sequence and heptamer sequence separated by a spacer region. There are two types of RSS, one with a spacer of 12 bp and one with a spacer of 23 bp. To ensure that segments are brought together in the right order, an RSS with a 12-bp spacer is always brought together with one with a 23-bp spacer. This is called the 12/23 rule. This ensures that in the heavy-chain locus, V rearranges to DJ and not directly to J or another V, and in the light-chain locus, V rearranges to J and not to another V.
True
With the exception of B cells, all other cells of the body have the immunoglobulin genes in the ______________.
a. germline configuration
b. monoclonal form
c. recombined configuration
d. expressed configuration
e. chimeric form
germline configuration
An individual with a genetic defect that results in a lack of somatic recombination between V, D, and J segments would be unable to rearrange either immunoglobulin or T-cell receptor genes somatically. There would be a severe combined immunodeficiency (SCID) owing to the absence of mature B cells and T cells.
True
In what way does the kappa light chain differ from the lambda light chain?
a. Kappa performs a different function from lambda when bound to the immunoglobulin heavy chain.
b. Kappa, but not lambda, is encoded on the same chromosome as the heavy-chain locus.
c. Kappa contains a VJ region, whereas lambda contains a VDJ region.
d. The kappa locus encodes a single C segment, whereas the lambda locus has more than one.
e. Kappa contains a transmembrane domain but lambda does not.
The kappa locus encodes a single C segment, whereas the lambda locus has more than one.
Linear epitopes are epitopes in proteins that comprise a contiguous amino acid sequence. They are also called continuous epitopes. In contrast, a conformational epitope is formed by amino acids that are brought together as a result of protein folding and are not adjacent in the protein sequence. Conformational epitopes are also known as discontinuous epitopes.
True
All of the following are utilized in the binding of antibodies to antigens, except ___________.
a. interchain disulfide bonds
b. hydrogen bonding
c. hydrophobic interactions
d. electrostatic forces (salt bridges)
e. van der Waals interactions
interchain disulfide bonds
Which of the following is not a component of V(D)J recombinase?
a. Artemis
b. Terminal deoxynucleotidyl transferase
c. RAG-1/RAG-2
d. DNA ligase IV
e. DNA-dependent protein kinase and the associated Ku protein
Terminal deoxynucleotidyl transferase
The name given to a fully activated and differentiated B cell that secretes antibody is __________________.
a. T cell
b. antigen-presenting cell
c. hematopoietic cell
d. secretory cell
e. plasma cell
plasma cell
All of the following comprise heavy-chain isotypes of immunoglobulin except _______.
a. alpha
b. beta
c. gamma
d. delta
e. epsilon
beta
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
e. antigenic determinants; complementarity determining regions
hypervariable loops; framework regions
Which of the following corresponds to the antigen-binding site of immunoglobulins?
a. VH:CH
b. VH:VL
c. VL:CL
d. CH:CL
e. VH:CL
VH:VL
Which of the following does not describe B-cell receptors?
a. B-cell receptors are membrane-bound and secreted.
b. B-cell receptors consist of a variable region and a constant region.
c. B-cell receptors lack specificity and can bind to a number of different antigens.
d. B-cell receptors possess specificity and can therefore bind only to unique epitopes.
e. B cell receptors undergo affinity maturation as a consequence of somatic hypermutation.
B-cell receptors lack specificity and can bind to a number of different antigens.
Which immunoglobulin is transported most efficiently across mucosal epithelium?
a. IgA
b. IgD
c. IgE
d. IgG
e. IgM
IgA
Which of the following determines the isotype of an immunoglobulin?
a. the composition of the hypervariable regions
b. whether the immunoglobulin is membrane-bound or secreted
c. its light chain
d. its heavy chain
e. the composition of the cytoplasmic tails of Ig? and Ig?
its heavy chain
The highest degree of diversity resulting from somatic recombination is concentrated ____________ of the VH and VL domains, whereas the point mutations caused by somatic hypermutation are found ____________.
a. in CDR3; throughout the V region
b. in CDR3; in CDR1 and CDR2 of VH and VL domains
c. in CDR1 and CDR2; in CDR3
d. in CDR1 and CDR2; throughout the V region
e. in all three CDRs; in C regions
in CDR3; throughout the V region
A newborn derives passive immunity from its mother as a result of placental transfer of _____ during pregnancy.
a. IgA
b. IgD
c. IgE
d. IgG
e. IgM
IgG
The mutational mechanism that results in the production of antibodies that bind antigen with higher affinity is called _____.
a. somatic recombination
b. isotype switching
c. somatic hypermutation
d. clonal selection
e. antigen processing
somatic hypermutation
Igalpha and Igbeta proteins are highly variable, because they interact directly with antigen. Igalpha and Igbeta perform specific signaling functions, which require particular amino acid sequences and also have evolved a sequence and structure that enable them to interact with all the different immunoglobulin isotypes. Extensive variation in Igalpha and/or Igbeta could therefore compromise their interaction with immunoglobulins and their signal transduction capabilities.
False
Igalpha and Igbeta are essential for escorting immunoglobulins from the endoplasmic reticulum membrane to the cell membrane, where they remain associated with the immunoglobulin to form the functional B-cell antigen receptor. The long cytoplasmic tails of Igalpha and Igbeta contain amino acid motifs that interact with intracellular signaling proteins after the receptor has been activated by the binding of antigen to the immunoglobulin.
True
The process of _____ results in the amplification of particular B cells with specificity for antigen.
a. germline recombination
b. somatic recombination
c. clonal selection
d. antigen processing
e. antigen presentation
clonal selection
As an adaptive immune response progresses, the production of variant antibodies that compete more effectively for antigen occurs, and B cells producing these antibodies are preferentially selected on the basis of their improved binding to antigen. This phenomenon is referred to as _______.
a. isotype switching
b. neutralization
c. allelic exclusion
d. affinity maturation
e. somatic rearrangement
affinity maturation
Which of the following statements about the production and use of monoclonal antibodies is incorrect?
a. Production of monoclonal antibodies requires a purified form of antigen.
b. A monoclonal antibody has specificity for only one epitope of an antigen.
c. B cells are fused with a tumor cell called a myeloma, to immortalize the resulting hybridoma.
d. Monoclonal antibodies made in mice have limited therapeutic potential.
e. Humanized monoclonal antibodies reduce complications associated with using mouse monoclonal antibodies.
Production of monoclonal antibodies requires a purified form of antigen.
The process used to produce either surface or secreted forms of the immunoglobulin heavy chain is called __________________.
a. alternative RNA processing
b. isotype switching
c. somatic recombination
d. somatic hypermutation
e. opsonization
alternative RNA processing
Naive B cells are recognized by their expression of ______________.
a. no immunoglobulins on the cell surface because somatic recombination has not yet commenced
b. both membrane-bound and secreted forms of immunoglobulin
c. both IgM and IgD on the cell surface
d. V(D)J recombinase
e. uracil-DNA-glycosylase (UNG)
both IgM and IgD on the cell surface
Which of the following can be found in serum in a monovalent form?
a. IgG4
b. IgD
c. IgA1
d. antibodies made up of four C domains
e. IgG3
IgG4
A circulating B cell that has never before encountered antigen expresses _____ on the cell surface.
a. IgM and IgD
b. IgM
c. IgD
d. IgM and IgG
e. IgG
IgM and IgD
The rejoining and repair of DNA during the recombination process leads to additional variation in sequence at the junctions between the rearranged gene segments. This is called junctional diversity and contributes considerably to the final diversity of T cell receptor specificities. Two sources of junctional diversity are introduced: P (palindromic) and N (nontemplated) nucleotides. P nucleotides are generated through endonuclease activity and repair around a hairpin loop at the ends of the gene segments to be joined. N nucleotides are nucleotides added at random at the junctions by terminal deoxynucleotidyl transferase (TdT) activity.
True
On the beta-chain gene locus, recombination signal sequences flank _______ of the V segment, _______ of the D segment, and _______ of the J segment.
a. the 5’ side; both sides; the 3’ side
b. the 5’ side; the 5’ side; the 5’ side
c. the 3’ side; both sides’; the 3’ side
d. both sides; both sides; both sides
e. the 3’ side; both sides; the 5’ side
the 3’ side; both sides; the 5’ side
IgG possesses _______ binding sites for antigen, and the T-cell receptor possesses _______ binding sites for antigen.
a. 1; 1
b. 2; 1
c. 1; 2
d. 2; 2
e. 2; 4
2; 1
The antigen-recognition site of T-cell receptors is formed by the association of which of the following domains?
a. Valpha and Calpha
b. Vbeta and Cbeta
c. Calpha and Cbeta
d. Valpha and Cbeta
e. Valpha and Vbeta
Valpha and Vbeta
In reference to the interaction between T-cell receptors and their corresponding ligands, which of the following statements is correct?
a. The organization of the T-cell receptor antigen-binding site is distinct from the antigen-binding site of immunoglobulins.
b. The orientation between T-cell receptors and MHC class I molecules is different from that of MHC class II molecules.
c. The CDR3 loops of the T-cell receptor alpha and beta chains form the periphery of the binding site making contact with the alpha helices of the MHC molecule.
d. The most variable part of the T-cell receptor is composed of the CDR3 loops of both the alpha and beta chains.
e. The most constant part of the T-cell receptor is composed of the CDR3 loops of both the alpha and beta chains.
The most variable part of the T-cell receptor is composed of the CDR3 loops of both the alpha and beta chains.
The CDR3 loops of the T-cell receptor contact the _______.
a. side chains of amino acids in the middle of the peptide
b. co-receptors CD4 or CD8
c. membrane-proximal domains of the MHC molecule
d. constant regions of antibody molecules
e. alpha helices of the MHC molecule
side chains of amino acids in the middle of the peptide
Which of the following statements regarding T-cell receptor recognition of antigen is correct?
a. alpha:beta T-cell receptors recognize antigen only as a peptide bound to an MHC molecule.
b. alpha:beta T-cell receptors recognize antigens in their native form.
c. alpha:beta T-cell receptors, like B-cell immunoglobulins, can recognize carbohydrate, lipid, and protein antigens.
d. Antigen processing occurs in extracellular spaces.
e. Like alpha:beta T cells, gamma:delta T cells are also restricted to the recognition of antigens presented by MHC molecules.
alpha:beta T-cell receptors recognize antigen only as a peptide bound to an MHC molecule.
How many complementarity-determining regions contribute to the antigen-binding site in an intact T-cell receptor?
a. 2
b. 3
c. 4
d. 6
e. 12
6
Which of the following statements regarding Omenn syndrome is incorrect?
a. A bright red, scaly rash is due to a chronic inflammatory condition.
b. Affected individuals are susceptible to infections with opportunistic pathogens.
c. It is invariably fatal unless the immune system is rendered competent through a bone marrow transplant.
d. It is the consequence of complete loss of RAG function.
e. There is a deficiency of functional B and T cells.
It is the consequence of complete loss of RAG function.
All of the following statements regarding gamma:delta T cells are correct except ___________.
a. they are more abundant in tissue than in the circulation
b. the delta chain is the counterpart to the beta chain in alpha:beta T-cell receptors because it contains V, D, and J segments in the variable region
c. they share some properties with NK cells
d. activation is not always dependent on recognition of a peptide:MHC molecule complex
e. expression on the cell surface is not dependent on the CD3 complex
expression on the cell surface is not dependent on the CD3 complex
Junctional diversity during gene rearrangement results from the addition of __________________.
a. switch region nucleotides
b. P and N nucleotides
c. V, D, and J nucleotides
d. recombination signal sequences
e. mutations in complementarity-determining regions
P and N nucleotides
If viewing the three-dimensional structure of a T-cell receptor from the side, with the T-cell membrane at the bottom and the receptor pointing upwards, which of the following is inconsistent with experimental data?
a. The highly variable CDR loops are located across the top surface.
b. The membrane-proximal domains consist of Calpha and Cbeta.
c. The portion that makes physical contact with the ligand comprises Vbeta and Cbeta, the domains farthest from the T-cell membrane.
d. The transmembrane regions span the plasma membrane of the T cell.
e. The cytoplasmic tails of the T-cell receptor alpha and beta chains are very short
The portion that makes physical contact with the ligand comprises Vbeta and Cbeta, the domains farthest from the T-cell membrane.
