Characterization of target antigens of the novel anti-mesangial cell antibodies in sera from patients with lupus nephritis

Abstract

Novel anti-mesangial cell antibodies have been identified in sera of majority patients with lupus nephritis in our previous study. The aims of current study were to investigate the association of anti-mesangial cell antibodies and anti-DNA antibodies, and whether the target antigens were on mesangial cell membrane. Affinity parified anti-DNA antibodies and sera with depletion of anti-DNA antibodies from three patients with lupus nephritis were used in Western-blot analysis to identify antigens in culture human glomerular mesangial cell line. Cell membrane from in vitro cultured human mesagial cell line was separated by gradient centrifugation technique, and the target antigens were identified by Western-blot analysis using 1% Triton X-100 solublized membrane protein as antigens and four known anti-mesangial cell antibody positive sera from patients with lupus nephritis as probes. Soluble proteins from in vitro cultured human mesangial cells could be blotted by both affinity purified anti-DNA antibodies (molecular weight at 63,000, 91,000 and 125,000) and sera with depletion of anti-DNA antibodies (molecular weight at 74,000 and 36,000). Proteins with molecular weight at 101,000, 91,000, 74,000 and 31,000 in mesangial cell membrane could be blotted by the four known anti-mesangial cell antibody positive sera. Some anti-mesangial cell antibodies were not associated with anti-DNA antibodies and anti-mesiangial cell antibodies could direct interact with antigens located on mesangial cell membrane. Anti-mesangial cell antibodies may play an important role in the pathogenesis of lupus nephritis.