SHARED IDIOTYPES IN MESANGIAL DEPOSITS IN IGA NEPHROPATHY ARE NOT DISEASE-SPECIFIC

The antigenic specificity of the mesangial IgA in IgA nephropathy (IgA N) remains unknown. Because shared antigenic specificities may be refl ected in the usage of shared idiotypes, we prepare five monoclonal ant i-idiotypic antibodies (MoAbs) specific for the mesangial IgA eluted f rom the kidney of an IgAN patient. All five MoAbs reacted with the sam e idiotype, which proved to be of a public nature. Although the idioty pe could be identified in the mesangial deposits of the majority Of Ig AN patients studied, it was not specific for the disease because it wa s also found in the glomerular deposits of other types of glomerulonep hritis. The idiotype was also expressed in polyethylene glycol precipi tates of sera and in pokeweed mitogen-induced plasma cells from both I gAN patients and healthy controls. The conclusion that no disease-spec ific idiotypes are present in the renal eluate was further supported b y the failure to produce polyclonal anti-idiotypic antibodies by immun izing a rabbit with the eluted mesangial IgA. Our results support the concept that mesangial IgA deposits in IgAN are of a polyclonal nature .