A human monoclonal hybridoma antibody (TrJ1) specific for HLA-DQ2

Influence on antibody recognition of amino acid substitutions in the cleft of HLA-DQ2 molecules. Suggestive evidence of peptide-dependent epitopes

The purpose of this study was to identify polymorphic residues of DQ2 beta chains which are involved in the epitopes recognized by DQ2-reactive mAbs. Binding studies were performed on a panel of DQ2 mutant cells made by transfection of a DQ (alpha 1*0501, beta 1*0301)-positive B-LCL with DQB1 genes encoding either wild-type or mutated DQ beta 1 *0202. Several aa substitutions were found to influence the binding of DQ2 mAbs. All but one of the mAbs were clearly sensitive to the introduced aa substitutions, but individual mAbs were differentially influenced, suggesting that they recognized different epitopes on the DQ2 molecule. Substitutions in positions 30 and 37 of the peptide-binding cleft were also found to influence the binding of some mAbs. Second, two mAbs, NFLD.M71 and NFLD.M102, which bound to DQ(alpha 1*0501, beta 1*0202) expressed in human cells and were sensitive to the introduction of aa substitutions in the cleft, bound weakly to the DQ(alpha 1*0501, beta 1*0202) heterodimer when expressed in a transfected murine NIH 3T3 cell line. Together this indicates that some DQ2-reactive mAbs may recognize peptide-dependent epitopes.

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

The cytotoxic IgM lambda human hybridoma mAb TrJ11 reacts with lymphoblastoid B-cell lines expressing DR4, DR8, DR11, and DRB1*1303. However, TrJ11 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 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 proved to be suitable for routine DR4 typing. The specific binding of TrJ11 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 possibility that amino acids located in the floor of the peptide-binding site are critical for the TrJ11 epitope is discussed.

A cytotoxic human hybridoma monoclonal antibody (TrJ5) specific for HLA-B38(16) and -B39(16)

We have generated a cytotoxic IgM lambda human hybridoma mAb (TrJ5), that is specific for HLA-B38(16) and -B39(16). Among a panel of 42 HLA-defined cell lines, TrJ5 killed all five B38-positive and both B16-positive cell lines, as well as the single B39-positive cell line, but not any cell lines lacking these antigens. It could be ruled out that the TrJ5 epitope is located on the alpha 1 domain because TrJ5 did not react with cells bearing HLA-B14, the alpha 1 domain of which is identical to alpha 1 of B39. In the alpha 2 domain of B38 and B39, a unique threonine residue at position 158 (Thr-158) is not shared by any of 29 other HLA-B alleles. This suggests that Thr-158 of the alpha 2-domain helix is critical for the TrJ5 epitope.