Common variable immunodeficiency with increased surface IgM-positive double-bearing B cells.

We report a case of common variable immunodeficiency (CVI) that shows low levels of IgG and IgA, but a normal quantitative or qualitative level of IgM. T-cell functions were not disturbed. Increased numbers of surface IgM (sIgM) and sIgD, sIgM and sIgG, sIgM and sIgA double-bearing B cells were observed as compared with a control. No IgG and IgA induction upon stimulation with Staphylococcus aureus Cowan I (SAC) and recombinant interleukin-2 (rIL-2), or pokeweed mitogen (PWM) and rIL-4 or rIL-6 was observed, although there was proliferation. Although mu mRNA was expressed as much as in a healthy control, transcription of gamma mRNA and alpha mRNA was very low. Furthermore, no enhanced effects of gamma mRNA and alpha mRNA were recognized upon stimulation with rIL-4 and rIL-6. These results suggest that the patient's B cells might be defective at the switching process from mu, mu and delta, mu and gamma to gamma or mu and alpha to alpha.