A HUMAN HYBRIDOMA MONOCLONAL-ANTIBODY (TRJ11) RECOGNIZING A NEW HLA-DR EPITOPE SHARED BY DR4, DR8, DR11, AND DRB1-ASTERISK-1303

The cytotoxic IgM lambda human hybridoma mAb TrJ11 reacts with lymphob lastoid B-cell lines expressing DR4, DR8, DR11, and DRB1()1303. Howev er, TrJ11 was monospecific when normal B cells freshly isolated from b lood served as targets in that it only killed HLA-DR4-positive cells. Thus, of 235 HLA-typed persons TrJ11 was strongly cytotoxic for normal B cells of all 90 DR4-positive individuals, but it did not react with B cells from any of the 145 DR4-negative donors. Hence, mAb TrJ11 pro ved to be suitable for routine DR4 typing. The specific binding of TrJ 11 to a DR4-positive cell line was profoundly blocked by the mouse HLA -DR beta chain-specific monomorphic mAb TAL 14. 1, indicating that the epitope recognized by TrJ11 is located in the DR beta chain. The poss ibility that amino acids located in the floor of the peptide-binding s ite are critical for the TrJ11 epitope is discussed.