Deck 8: Humoral Immune Responses

Question 1

A 5-year-old boy has a history of recurrent pneumococcal pneumonia,Pneumocystis carinii pneumonia (PCP),and bacterial ear infections.His maternal uncle and an older brother experienced the same symptoms,but he has an older sister who is healthy.Laboratory studies indicate normal numbers of B cells and T cells,and the serum contains mostly IgM and very little IgG.Which of the following abnormalities would NOT be likely in this patient?

A)The IgG antibodies that are present are of lower affinity for antigen than of those of a healthy individual.
B)Lymph nodes are without well-developed follicles containing germinal centers.
C)Macrophage killing of intracellular microbes is impaired.
D)There is limited diversity in the repertoire of IgM antibodies produceD.
E)There is no evidence of somatic mutation of IgM variable regions.

Answer 1

There is limited diversity in the repertoire of IgM antibodies produceD.

Question 2

Antibody feedback is mediated by which of the following molecules?

A)Ig Fc $\gamma$ RIIB
B)Ig Fc?
C)Ig $\gamma$ RI
D)CR1
E)IgM

Answer 2

Ig Fc $\gamma$ RIIB

Question 3

Which one of the following statements about primary and secondary antibody responses is NOT true?

A)Antibodies in primary responses generally have lower affinity for antigen than those produced in secondary responses.
B)Secondary responses reach peak levels more quickly than primary responses.
C)Primary responses require higher concentrations of antigen for initiation than secondary responses.
D)Primary responses occur to all types of antigens,but secondary responses mostly occur only to protein antigens.
E)Primary responses are characterized by IgG antibodies,whereas secondary responses are dominated by IgM antibodies.

Answer 3

Primary responses are characterized by IgG antibodies,whereas secondary responses are dominated by IgM antibodies.

Question 4

A 5-year-old boy has a history of recurrent pneumococcal pneumonia,Pneumocystis carinii pneumonia (PCP),and bacterial ear infections.His maternal uncle and an older brother experienced the same symptoms,but he has an older sister who is healthy.Laboratory studies indicate normal numbers of B cells and T cells,and the serum contains mostly IgM and very little IgG.If this patient did have a sister affected with the same condition,which of the following genes would most likely contain a mutation?

A)AID (activation-induced deaminase)
B)CD40
C)CD40L
D)CD28
E)CTLA-4

Question 5

Which of the following events does NOT occur within germinal centers?

A)Somatic mutation of Ig V genes
B)Generation of memory B cells
C)B cell proliferation
D)Affinity maturation
E)Ig gene V(D)J recombination

Question 6

Which one of the following statements about humoral immune responses is true?

A)Naive B cells are required for initiation of primary responses and memory B cells are required for initiation of secondary responses.
B)Antibody responses to bacterial polysaccharide antigens require CD4⁺ helper T cells.
C)Heavy chain isotype switching typically occurs in response to bacterial polysaccharide antigens.
D)Affinity maturation does not require helper T cells.
E)Antibody-secreting cells generated during a humoral immune response live for only a few hours.

Question 7

The B cell receptor (BCR)complex and the signaling cascades to which it is linked share many similarities with the T cell receptor (TCR)complex and its linked signaling cascades.Which of the following comparisons between BCR and TCR signaling is NOT true?

A)There are ITAMs in the cytoplasmic tails of CD3 in the TCR complex and in the cytoplasmic tails of Ig $\alpha$ and Ig $\beta$ in the BCR complex.
B)The cytoplasmic tails of membrane Ig and TCR $\alpha$ antigen receptors are very short and lack intrinsic signaling functionality.
C)Early signaling events induced by antigen binding to both BCR and TCR involve both Src family and Zap-70 family protein tyrosine kinases.
D)Phospholipase C-mediated generation of IP₃ and DAG occurs downstream of both BCR and TCR signaling.
E)CD4/CD8 coreceptors in T cells and the CR2 coreceptor in B cells both enhance responses to antigen by a PI3 kinase-dependent mechanism.

Question 8

Which of the following statements about Ig isotype switching is NOT true?

A)Interleukin-4 promotes switching to the IgE isotype by increasing germline transcription of the C? exon.
B)Isotype switching involves recombination of a V(D)J complex with downstream C region genes and the deletion of intervening DNA including other C region genes.
C)Activation-induced deaminase (AID)is required for switch recombination.
D)The enzymes that mediate isotype switching recognize conserved heptamer and nonamer DNA sequences adjacent to the constant region exons.
E)The same recombined V(D)J gene complex is used to encode the antigen-binding region of the antibodies produced by a B cell before and after isotype switching.

Question 9

Which of the following descriptions about affinity maturation is correct?

A)Depends on somatic mutation of V genes
B)Depends on negative selection of B cells that can bind antigen in the germinal center
C)Depends on antigen processing and presentation by dendritic cells within the germinal center
D)Depends on the autoimmune regulator (AIRE)gene
E)Depends on somatic recombination of Ig V genes

Question 10

Which one of the following molecules is important for the production of IgE antibodies?

A)CD28
B)CD40
C)IFN- $\gamma$
D)IL-2
E)TGF- $\beta$

Question 11

Which one of the following B cell responses is NOT stimulated by CD40 ligand?

A)Association of TRAFs with the cytoplasmic tails of CD40 molecules
B)Activation of NF- $\kappa$ B
C)Enhanced expression of B7-1 and B7-2
D)Enhanced Ig isotype switch recombinase activity
E)Enhanced production of membrane Ig

Question 12

Which one of the following statements accurately describes antigen recognition events in a lymph node during a helper T cell-dependent antibody response to a protein antigen?

A)Naive B cells and naive T cells simultaneously recognize the intact protein antigen.
B)Naive B cells recognize intact proteins,generate peptide fragments of these proteins,and present them in complexes with major histocompatibility complex (MHC)molecules to naive helper T cells.
C)Naive B cells recognize intact proteins,generate peptide fragments of these proteins,and present them in complexes with MHC molecules to differentiated helper T cells.
D)Naive T cells recognize peptides bound to MHC molecules presented by dendritic cells,and naive B cells recognize the intact protein antigen bound to the surface of follicular dendritic cells.
E)Differentiated helper T cells recognize peptides bound to MHC molecules on dendritic cells,and the T cells secrete cytokines that promote antibody production by any nearby B cells that have recognized different protein antigens.

Question 13

All of the following assays are used to detect antibody production EXCEPT:

A)BrdU (bromodeoxyuridine)assay
B)Enzyme-linked immunosorbent assay (ELISA)
C)ELISPOT assay
D)Hemolytic plaque assay
E)Radioimmunoassay (RIA)

Question 14

The initial cellular events that are induced by antigen-mediated cross-linking of the B cell receptor (BCR)complex include all of the following EXCEPT:

A)Increased percentage of time spent in mitosis,resulting in rapid proliferation
B)Increased expression of B7,resulting in enhanced APC function
C)Increased expression of bcl-2,resulting in improved survival
D)Increased expression of CCR7,promoting migration into lymph node follicles
E)Increased expression of the interleukin-2 receptor,resulting in enhanced proliferation and response to T cell signals

Question 15

Which of the following antigenic structures might activate B cell antibody production without the aid of T cells?

A)Lysozyme
B)Benzene
C)Glucose-6-phosphate
D)ABO blood group antigen
E)Rh factor antigen

Question 16

Which of the following mechanisms contributes to the change from B cell production of membrane Ig to secreted Ig?

A)V(D)J recombinase-mediated deletion of the exon encoding the transmembrane domain
B)Alternative processing of primary RNA transcripts to remove the transmembrane domain and include a secretory tail piece
C)Increased vesicular exocytosis of intracellular stores of the secretory form of Ig
D)Switch recombinase-mediated recombination of the heavy chain locus to juxtapose the V(D)J segment with the exon encoding a secretory tail piece
E)Up-regulation of ectoenzymes that proteolytically cleave membrane Ig heavy chains just proximal to the membrane

Question 17

A 5-year-old boy has a history of recurrent pneumococcal pneumonia,Pneumocystis carinii pneumonia (PCP),and bacterial ear infections.His maternal uncle and an older brother experienced the same symptoms,but he has an older sister who is healthy.Laboratory studies indicate normal numbers of B cells and T cells,and the serum contains mostly IgM and very little IgG.Which of the following genes most likely contains a mutation in this patient?

A)AID (activation-induced deaminase)
B)CD40
C)CD40L
D)CD28
E)CTLA-4