A 5-Year-Old Boy Has a History of Recurrent Pneumococcal Pneumonia,Pneumocystis

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.