Chat with AIExam 11: Immunological Memory and Vaccination
Explain (A)why only memory B cells,and not naive B cells,participate in secondary immune responses to particular pathogens,and (B)why this is advantageous to the host.
(33) 
Verified A. Naive B cells carry the inhibitory Fc receptor FcγRIIB1. Complexes composed of antigen and IgG produced in the primary response, or by reactivated memory cells, cross-link FcγRIIB1 and the B-cell receptor, which suppresses naive B-cell activation. In contrast, memory B cells do not carry this receptor, and so are not inhibited in this way.
B. The suppression of naive B cells means that only reactivated memory B cells (which have already undergone isotype switching and somatic hypermutation) make antibodies. Thus all the antibodies made are of high affinity and are primarily of the IgG, IgA, or IgE isotype. Suppression of naive B cells eliminates repetition of the events that took place in the primary immune response, which would, if not inhibited, lead to the production of low-affinity IgM antibodies rather than high-affinity, isotype-switched antibodies that are more effective at removing the pathogen.
_____ involves deliberate stimulation of the immune system and induction of protective immunity to a particular disease-causing pathogen by mimicking infection in the absence of disease.
(36) VerifiedC
B cells are activated by CD4 TH2 cells only if both cell types recognize the same antigen.The same epitope,however,does not need to be shared for recognition.
A.Discuss why this characteristic is important in vaccine design.
B.Provide an example of a conjugate vaccine used to stimulate the synthesis of IgG antibody against Haemophilus influenzae B polysaccharide.
(31) VerifiedA. Many bacteria are surrounded by a polysaccharide capsule. In some cases, antibodies against the capsular polysaccharides give protective immunity against the pathogen. Antibodies produced against polysaccharide antigens are generally restricted to the IgM isotype, because the help needed to switch isotypes to IgG is provided by T cells, which recognize only peptide antigens. Adult humans make effective immune responses to polysaccharides alone and thus can be protected by subunit vaccines made from the capsular polysaccharides of encapsulated bacteria. Their antibody responses are polysaccharide-specific, T-cell independent, and involve antibodies of the IgM isotype. In contrast, children do not make effective immune responses to polysaccharides alone and thus cannot be immunized with such vaccines.
However, if the polysaccharide is conjugated to a protein, peptides from the protein part of the molecule can activate specific TH2 cells. B cells specific for polysaccharide will bind and internalize the whole antigen via their antigen receptors, process it, and then present peptides from the protein part on their surface. T cells specific for these peptides will interact with the B cell, delivering the necessary cytokines (such as IL-4) and the CD40–CD40-ligand signal required for isotype switching. The B cell will then produce IgG anti-polysaccharide antibodies. This type of vaccine can be used to immunize children so as to induce protective anti-polysaccharide antigens.
B. A vaccine of this type has been produced against Haemophilus influenzae B (HiBC), which can cause pneumonia and meningitis. The conjugate vaccine is composed of a capsular polysaccharide of H. influenzae conjugated to tetanus or diphtheria toxoid (a protein). The antibody response is polysaccharide-specific, T-cell dependent, and comprises IgG that protects children from the meningitis caused by this microorganism.
Which of the following vaccines is least likely to pose a risk in an individual with an immunodeficiency?
(37) An example of an inactivated virus vaccine is _____.(Select all that apply.)
(31) In the context of providing protection against smallpox,describe (A)the similarities and (B)the differences between variolation and vaccination.(C)Now explain the mechanisms by which immunization with vaccinia virus provides protection against smallpox.
(28) The efficiency and specificity of adaptive immune defenses and immunological memory improve each time a particular pathogen is encountered because _____.
(34) All of the following are ways in which plasma cells differ from memory cells except _____.
(39) The reason that vaccines against influenza must be administered annually,unlike vaccines against measles,is _____.
(37) Recombinant DNA technology has been especially useful for the production of _____ that are used in subunit vaccines.
(37) Verified (32) Imagine a situation in which an individual who has a latent cytomegalovirus (CMV)infection receives a hematopoietic stem-cell transplant.Which of the following is likely to occur?
(28) Which of the following explain why the safety standards for vaccines are set higher than those for drugs? (Select all that apply.)
(35) A newly identified antigen protein of Neisseria meningitidis called fHbp increases virulence by _____.
(29) A conjugate vaccine is one that couples _____ to _____ so as to stimulate T-dependent antibody responses.
(33) Which of the following explains why the first baby born to a RhD- mother and a RhD+ father does not develop hemolytic disease of the newborn?
(37) Which of the following molecules is not elevated on the surface of memory B cells compared with naive B cells?
(35) _____ is the approach that mines a pathogen's genome to reveal potential antigens and derives clues about cellular location,function,and ability to stimulate protective antibodies based on nucleotide sequence.
(35) 
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