A human hybridoma monoclonal antibody (TrJ11) recognizing a new HLA-DR epitope shared by DR4, DR8, DR11, and DRB1∗1303

Abstract The cytotoxic IgMλ human hybridoma mAb Trj11 reacts with lymphoblastoid B-cell lines expressing DR4, DR8, DR11, and DRB1 ∗ 1303. However, TrJ 11 was monospecific when normal B cells freshly isolated from blood served as targets in that it only killed HLA-DR4-positive cells. Thus, of 235 HLA-typed persons TrJ 11 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 TrJ 11 proved 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-DRβ chain-specific monomorphic mAb TAL 14.1, indicating that the epitope recognized by TrJ 11 is located in the DRβ chain. The possibility that amino acids located in the floor of the peptide-binding site are critical for the Trj11 epitope is discussed