Downregulation of a pathogenic autoantibody response by IgM autoantibodies directed against the nephritogenic antigen in slowly progressive Heymann nephritis.

The purpose of the study was to find out if a new modified vaccination technique would be effective in downregulating immunopathological events during the course of an experimental autoimmune kidney disease (which is morphologically and functionally similar to Heymann nephritis) called 'slowly progressive Heymann nephritis' (SPHN). We have shown that the pathogenic IgG autoantibody (aab)-induced experimental autoimmune kidney disease process can be downregulated early on as well as during the chronic progressive phase, when rats were restimulated. The IgM aab, resulting from stimulation by immune complexes made up of rat kidney fraction 3 (rKF3) antigen and rat anti-rKF3 IgM antibody in antigen excess (MIC), can greatly diminish pathogenic aab production by removing or blocking nephritogenic antigens. Reduced IgG aab production limits the formation of damaging immune complexes (IC) in the glomeruli and development of proteinuria. At the end of the experiment 60% and 80% of the MIC-treated groups had no pathogenic IgG aab in their circulation, while all the untreated SPHN rats had high levels of IgG aab associated with disease progression manifesting in increased proteinuria and severe immune complex glomerulonephritis.