CROSS-REACTIVITY OF THE B/B'-SUBUNIT OF THE SM RIBONUCLEOPROTEIN AUTOANTIGEN WITH PROLINE-RICH POLYPEPTIDES

Using recombinant fusion proteins representing different regions of the human Sm B B′ polypeptide, the 4B4 monoclonal anti-Sm antibody was found to bind a C-terminus epitope that is proline-rich. 4B4 cross-reacted with the p24 gag protein of HIV-1 and with other polypeptides rich in proline residues, including collagen. BALB c mice immunized with human collagen not only produced antibodies to the immunizing antigen but also antibodies to Sm. This immune mouse serum also recognized C-terminus B B′ fusion proteins. These data suggest that the Sm B B′ antigen contains a poly-Pro epitope that is shared by several autoantigens and retroviral proteins. These sites may be important in the induction of autoantibodies through molecular mimicry. © 1992.