Which is the most likely reason that HIV-infected people with heterozygous HLA loci have a delayed progression to AIDS compared with patients who are homozygous at one or more HLA loci?
a. The greater number of HLA alleles provides a wider variety of HLA molecules for presenting HIV-derived peptides to CD8 T cells even if HIV mutates during the course of infection.
b. Heterozygotes have more opportunity for interallelic conversion and can therefore express larger numbers of MHC alleles.
c. Directional selection mechanisms favor heterozygotes and provide selective advantage to pathogen exposure.
d. As heterozygosity increases, so does the concentration of alloantibodies in the serum, some of which cross-react with and neutralize HIV.
A
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