IMMUNOLOGICAL MIMICRY BETWEEN RETINAL S-ANTIGEN AND GROUP-A STREPTOCOCCAL M-PROTEINS

Immunological mimicry between host and microbial proteins has been sug gested as a potential mechanism in the development of uveitis in human s. In this study immunological corssreactivity between anti-streptococ cal monoclonal antibodies (MAbs) and the human eye was investigated. I n indirect immunofluorescence, we demonstrated novel immunological cro ssreactivity of two antistreptococcal MAbs (27 and 112) with the rod o uter (and inner) segments of the retina of the human eye. In further s tudies, retinal S-Ag, a uveitogenic protein in the rod outer (and inne r) segments, was found to react with the anti-streptococcal MAbs. In a ddition, several uveitogenic peptides of S-Ag were recognized by the a nti-streptococcal MAbs. In the ELISA and Western immunoblot, anti-S-Ag MAbs crossreacted with group A streptococci and the streptococcal M p rotein Further demonstrating sites of antigenic similarity. Homology b etween the retinal S-Ag and streptococcal M protein was observed in am ino acid sequences repeated in the B repeat region of the streptococca l M5 protein. These data show that retinal S-antigen has immunological similarities with streptococcal M protein, a major virulence determin ant and strong bacterial cell surface antigen.