1. True/False: Once B cells begin secreting antibodies, they cease dividing and
ID: 219516 • Letter: 1
Question
1. True/False: Once B cells begin secreting antibodies, they cease dividing and have a life-span of only a few days.
2. In germinal centers, proliferating B cells undergo a process called somatic hypermutation, in which mutations are introduced into the V regions of the antibody heavy and light chain genes. When this process is complete after several weeks, the overall affinities of the antibodies produced are greatly increased compared to those present early in the primary response. The somatic hypermutation process leads to increased antibody affinity because:
A. Mutations that decrease the antibody affinity lead to an arrest of B cell proliferation.
B. B cells making higher affinity antibodies receive more help from TFH cells.
C. Somatic hypermutations only take place in the sequences encoding the CDR1, CDR2, and CDR3 regions.
D. Mutations that increase antibody affinity lead to an increased rate of B cell proliferation.
E. The majority of nucleotide changes introduced by AID don’t change
the amino acid coding sequence
3. In humans, IgA is produced in copious amounts, estimated to be a rate of 3 g/day. Nearly all of the IgA secreting plasma cells are found in the gastrointestinal (GI) tract where the secreted IgA is transported across the GI epithelium into the lumen of the gut. There, this antibody protects the GI epithelium against intestinal pathogens. In contrast, none of the GI resident long-lived antibody secreting cells produce antibodies of the IgG class. The differential localization of long-lived antibody secreting cells producing IgA compared to those producing IgG is likely due to:
A.Their interactions with TFH cells specific for pathogens that infect the gut
B.The lack of germinal centers in the mucosal lymphoid organs
C.The absence of S1PR1 expression on IgA-secreting plasma cells
D.Their priming and differentiation in mucosal lymphoid organs
E.Their inability to access the bone marrow compartment
Explanation / Answer
1.Ans- False
Memory B cells produce high-affinity antibodies in response to antigen and have a long-lived lifespan.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.