Defective B cell function associated with inherited interstitial deletion of the short arm of the X chromosome.

The B cell function of a patient with low serum immunoglobulin (Ig) levels and with an interstitial deletion in the short arm of one of her X chromosomes (del(Xp] and the B cell function of her relatives were analyzed by indirect protein A plaque-forming cell (PFC) assay and by measuring immunoglobulin secretion in vitro by ELISA. B cells were activated by pokeweed mitogen (PWM) with or without hydrocortisone (HC) to inhibit HC-sensitive suppressor cells. The patient, her mother, and one sister, all of them having del(Xp), generated very few PFC induced by PWM, even in the presence of HC, whereas normal PFC responses were found in the patient's cytogenetically normal sisters. The B cells of the subjects with del(Xp) secreted very low amounts, if any, of IgA, IgG, and IgM. Co-culture experiments with B cells from del(Xp) subjects and normal OKT 4+ cells revealed no or very low Ig production. The function of the del(Xp) subjects' OKT 4+ cells was slightly reduced, whereas the activity of their OKT 8+ cells was normal. The cell subset analysis in the peripheral blood revealed decreased OKT 4+:8+ ratios in all del(Xp) subjects. The results indicate an intrinsic B cell defect with a possible concomitant immunoregulatory defect associated with del(Xp). Moreover, the results support the hypothesis that antibody production is at least partially controlled by genes located in the short arm of the X chromosome.