In vivo alteration of antibody production in patients with IgA nephropathy.
Augmentation of IgA production has been postulated for the development of IgA nephropathy. An influenza HA vaccine was administered to healthy adults and patients with IgA nephropathy to elucidate if there was any in vivo alteration of antibody production in response to antigenic stimulation in these patients. The vaccine was administered s.c. in a dose of 350 CCA units at an interval of 4 weeks. IgG, IgA and IgM class antibodies to influenza HA antigens and three classes of rheumatoid factors (RF) were determined using a solid phase fluorescence immunoassay. The titres of IgG class antibodies to influenza HA antigens did not change significantly in either group after the vaccination. No significant differences were observed in the titres of IgG antibodies between the two groups. IgA antibodies were significantly increased only in patients in the 4th week and continued to the 8th week. The titres of IgA antibodies were always higher in patients than in controls during the study period. IgM antibodies were significantly increased stepwise in both groups to an equal degree. IgG and IgA RF were always higher in patients than in controls. IgM RF were significantly increased and higher than in controls in the 8th week in patients. It is concluded that patients with IgA nephropathy might be high responders for IgA antibody production, and that polyclonal activation might be associated with increased IgA production following in vivo antigenic stimulation in these patients.