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
ANS;A
Somatic mutation of V genes is the basis for production of immunoglobulins with different affinities,which are then positively selected in the germinal center;B cells that cannot bind antigen with high affinity die through a default pathway of apoptosis.Antigen processing and presentation by dendritic cells are required to generate helper T cells outside the follicle,but not to activate B cells in the folliclE.Autoimmune regulator (AIRE)is involved in thymic expression of tissue antigens but is not involved in affinity maturation.Somatic recombination of V genes is involved in producing functional Ig genes during B cell development,but it is not involved in germinal center reactions.
