Human monoclonal antibodies: analysis of two antibodies derived from lymphocytes of a patient with acute rheumatic fever.

: Human monoclonal antibodies were produced by fusion of peripheral blood lymphocytes from a patient with acute rheumatic fever, with the HGPRT-non-secreting murine (Balb-c) cell line SP2/0Ag14. Heterohybridomas were selected by screening against rheumatic fever-associated group A streptococci using an ELISA, and against paraffin wax-embedded human heart sections using an immunoperoxidase technique. Two human IgM monoclonal antibodies were selected for further analysis by Western blotting and ELISA. Both antibodies demonstrated multispecificity by immunoblotting and ELISA. One of the monoclonals bound to 48 kD and 83 kD bands common to group A streptococcal and heart antigen preparations. Both human monoclonal antibodies bound to a 43 kD constituent band common to human heart and sarcolemma membrane extract. Inhibition studies performed using a competitive solid phase immunoassay confirmed shared epitopes between group A streptococci and human heart. The significance of these monoclonal antibodies to the pathogenesis of rheumatic fever is uncertain.