ACTIVATION OF A MURINE AUTOREACTIVE B-CELL BY IMMUNIZATION WITH HUMANRECOMBINANT AUTOANTIGEN LA SS-B - CHARACTERIZATION OF THE AUTOEPITOPE/

Immunization of Balb/c mice with a homogeneously purified recombinant human La/SS-B protein resulted in activation of an autoreactive B cell secreting a novel monoclonal anti-La antibody termed La4B6. La4B6 rea cted with La protein from a variety of sources including human, bovine , rat and mouse. ATP blocked the binding of La4B6 to recombinant La pr otein. The human epitope was identified as consisting of the amino aci d sequence SKGRRFKGKGKGN, which includes the proposed ATP-binding site of the La protein. In the human and bovine La protein, the epitope ex ists as a continuous amino acid sequence. In rat and mouse the epitope was found to consist of the amino acid sequence SKG interrupted by a species-specific insert of 16 amino acids, and followed by the second half of the epitope, the amino acid sequence RRFKGKGKGN. Our data sugg est that in the case of the rat and mouse La proteins the two separate d parts of the epitope are able to form a conformational epitope which looks similar to the continuous human epitope. (C) 1995 Academic Pres s Limited