Prozone Effects in Indirect Immunofluorescence

Abstract

A marked prozone effect was observed in indirect immunofluorescence (IFL) with rabbit antisera against rat renal proximal tubular epithelial brush border (BB) antigens; anti-BB antibodies were not detectable if used in high concentrations, but were readily demonstrated if sufficiently diluted. The prozone effect occurred in spite of demonstrated binding of anti-BB antibodies to target antigens. No prozone was seen when direct IFL was used, and cross-reacting antigens in small-intestinal epithelial brush border were detectable by indirect IFL without prozone. The anti-immunoglobulin conjugates were unable to reach antigenic determinants on tightly clustered immunoglobulin molecules. Prozone effects seem to depend primarily on the density of antigen determinants in the target tissues.