Circulating Autoantibodies to Mammalian Tissue Kallikreins 1

Abstract

Abstract

Autoantibodies to tissue kallikrein (EC 3.4.21.35) were discovered in normal human, rat, mouse, and guinea pig sera. Three independent methods—binding of iodolabeled antigen, enzyme—linked immunosorbent assay (ELISA), and immunoblotting—were used to demonstrate these kallikrein autoantibodies. Autoantibodies from rat and human sera were purified, using rat and human tissue kallikrein-affinity chromatography, respectively. Purified rat kallikrein autoantibody bound 50% of ¹²⁵I-labeled rat urinary kallikrein upon incubation of antibody at 2.5 × 10⁻¹⁰ M. The subtypes of rat and human kallikrein autoantibodies were determined by an ELISA, using antisera to immunoglobulin subclasses. In both species, autoantibody was predominantly IgG (~80%) and some IgM (~20%). Purified autoantibodies from rat and human sera were separated on sodium deodecyl sulfate-polyacrylamide gels, and their subunits were identified by Western blot analyses, using anti-rat and anti-human IgG antibodies, respectively. When primary cultures of mouse spleen cells were incubated for 1 to 5 days with lipopolysaccharide (1 to 5 μg/ml), the anti-kallikrein antibodies in the media increased up to seven-fold. We have demonstrated circulating autoantibodies that recognize and bind both autologous and heterologous kallikrein; however, their significance to the function of the tissue kallikrein-kinin system in normal and disease states remains to be explored.