A new murine lymphocytotoxic monoclonal antibody recognizing HLA-A2, -A28 and -A9

Monoclonal antibodies recognizing polymorphic as well as monomorphic epitopes on HLA antigens are important tools for understanding the immuno-biology of HLA molecules. We immunized BALB/c mice with a HLA-A2 transfectant and screened for hybridomas which reacted with a HLA-A2 trans-fectant but not with a HLA-B75 transfectant. After subcloning by limiting dilution four times, a hybridoma secreting a monoclonal antibody (mAb) (IgG 2a, kappa) designated 1–145 was established. 1–145 reacted with Epstein-Barr virus transformed B lymphoblastoid cell lines (B cell lines) which expressed HLA-A2, -A28, -A23 and -A24. The titer of 1–145 in culture supernatant against HLA-A2 and -A28 antigens was similar and the titer against HLA-A23 was lower. 1–145 reacted with cells expressing HLA-A24 but the titer against HLA-A24 antigens was even lower than that againt HLA-A23 antigens. The HLA-A24 antigens on the peripheral blood lymphocytes were not detected by 1–145 possibly due to the lower expression compared to the B cell lines. These differences of the titers were reflected to microlymphocytotoxic-ity assay in which 1–145 culture supernatant lysed all PBLs expressing HLA-A2.-A28 and -A23 but did not lyse PBLs expressing HLA-A24. Published deduced amino acid sequence data of HLA class I molecules indicate that Lys in position 127 may be critical for 1–145 binding.