Inability to detect circulating anti‐idiotypic antibodies in human anti‐GBM antibody‐mediated disease using a splenic PFC assay

Abstract

Anti-idiotypic antibodies are antibodies that are directed against the variable region of the corresponding antibody molecule and have been postulated to have a regulatory role in the immune response. Circulating anti-idiotypic antibodies have been reported in several antibody-mediated autoimmune diseases. We have established the following detection system for anti-idiotypic antibodies in human anti-glomerular basement membrane (GBM) disease. Spleen cells harvested from BALB/c mice immunised with human GBM were incubated with GBM-coated sheep red blood cells in the presence of guinea pig complement. Each spleen cell that produced anti-GBM antibodies resulted in a surrounding plaque where antibodies lysed the GBM-coated RBC. The number of plaques could be inhibited by the addition of heterologous anti-idiotypic antibodies to the plaquing mixture. Anti-idiotypic antibodies were then sought in both acute and convalescent phase sera from patients with anti-GBM disease and in laboratory staff who repeatedly handled GBM and sera containing anti-GBM antibodies. Anti-GBM antibodies were removed from all material before testing and affinity-purified preparations contained concentrations of IgG corresponding to the range that resulted in inhibition when affinity-purified rabbit anti-idiotypic antibody was examined. No anti-idiotypic antibodies could be demonstrated in any of the sera or IgG preparations examined. We conclude that if circulating anti-idiotypic antibodies are present in patients with anti-GBM disease, they must be infrequent, or at concentrations below the limits of detection of this assay (less than 1 mcg/mL). The observations of anti-idiotypic antibodies in other antibody-mediated diseases need to be confirmed.