MOLECULAR ANALYSIS OF V-GENE-SEQUENCES ENCODING CYTOTOXIC ANTI-STREPTOCOCCAL ANTI-MYOSIN MONOCLONAL-ANTIBODY 36.2.2 THAT RECOGNIZES THE HEART CELL-SURFACE PROTEIN LAMININ/

Anti-streptococcal/anti-myosin mAb 36.2.2 is unique among the cross-re active anti-streptococcal mAbs due to its cytotoxicity for rat heart c ells and its ability to strongly label the surface of heart cells in i ndirect immunofluorescence assays. In this study, cytotoxic mAb 36.2.2 was found to react strongly with the extracellular matrix protein lam inin in immunoblots and inhibition assays, while 11 other cross-reacti ve anti-streptococcal mAbs did not react with laminin and were not cyt otoxic, Cytotoxicity appeared to correlate with the presence of lamini n on the surface of cells, Heavy and light, chain variable region gene s encoding mAb 36.2.2 were highly homologous to other V genes encoding anti-carbohydrate and/or autoantibodies. V-H, J(H), and J kappa segme nts of mAb 36.2.2 may be encoded by germline gene segments. The V-H se gment may be identical with an as yet unidentified V(H)7183 family ger mline sequence, and the 36.2.2 V kappa region gene is encoded by a V k appa 8 family member.