RG1, A NEW MURINE MONOCLONAL-ANTIBODY RECOGNIZING A SUPERTYPIC DETERMINANT ON HLA-A MOLECULES

Monomorphic and polymorphic anti-HLA monoclonal antibodies (mAb) are v aluable reagents for assessment of the structural and functional impor tance of different class I determinants. We have generated a new mAb, RG1, reacting with an epitope variably expressed on normal and leukemi c hematopoietic cells of different lineages. Immunoprecipitation of th e RG1 antigen disclosed a bimolecular complex characteristic of class I proteins. The RG1 epitope was expressed on an HLA-A2 transfected cel l line but not on cells transfected with HLA-E, -F or -G molecules. MA b reactivity with reference B-lymphoblastoid cell lines and HLA typing of RG1 reactive and unreactive cells demonstrated that the epitope wa s expressed in conjunction with defined HLA-A molecules. Cells express ing HLA-A2, -A24(9) and -A68(28) proteins were brightly stained with R G1 whereas mAb binding to HLA-A1, -A11 and a split of A3 molecules was significantly lower. In contrast, the RC1 epitope was apparently not expressed on HLA-A23(9), -A25(10), -A26(10), A29(19), -A30(19), -A31(1 9), -A32(19), -A33(19) and some HLA-A3 molecules. Based on class I a s equence data, these results suggest that the RG1 epitope is localized to a region of the alpha 2 helix accessible to the T cell receptor for antigen on cytotoxic T lymphocytes. Lys in position 144 and His in po sition 151 are apparently critical for RG1 binding.