Recognition of HLA-DR1/DRB1 *0101 molecules presenting HLA-A2 derived peptides by a human recombinant antibody, Fab-5 A1

Abstract

MHC molecules present peptides in their binding groove to T-cell receptors inducing proliferation or cytotoxicity of alloreactive T cells. A previously generated human monoclonal antibody (mAb) UL-5 Al, recognizing a conformationa l epitope formed by HLA DRl/DRBl *0101 molecules and HLA-A2 derived peptides, demonstrates Tcell-like recognition of the peptide/MHC complex (PMC). To stud y the genes of the antigen binding region, the nucleotide sequences of the rearranged genes in the variable regions of UL-5 Al were determined and the Yge.ne usage (VH3, YA2) was identified by comparison With publi hed germlines. The genes encodi ng heavy (Fd) and light (L) chains of UL-5 A 1 were linked and expressed in a bacterial system. Specificity of the reco mbinant Fab-5 A 1 was determined with HLA -typed LCLs by ~ow cytometric analysis. As demonstrated in competitive 1111 'b' . 1 • 1t1on as ays, UL-5 Al and Fa b-5 A 1 recogni ze the sa me PM epitope on HLA-A2+, -DR 1/DRBl *0101 + typed L Ls. Additionally, mAb UL-5 Al and Fab-5 Al both recognize HLA-Ar, -DRl/DRBl *OlOr LCLs exogenously loaded with HLA-A2 peptides (105-11 7, 103-11 7). UL-5 Al -like antibodies again t peptide/MH complexes could prove va luable tools for research on Tcell recognition and MH fun ction.