Interestingly, among the 32 CVID patients in whom both PnP antibodies and isoagglutinins could be tested, nine patients showed no detectable isoagglutinins and no or only very low blood group anti-A/B antibodies in the SPR assay and also showed no PnP-specific IgM-antibody response. The gene discussed is PNP; the disease is common variable immunodeficiency.