CHARACTERIZATION AND EPITOPE MAPPING OF 4 HLA CLASS-II REACTIVE MOUSEMONOCLONAL-ANTIBODIES USING TRANSFECTED L CELLS AND HUMAN-CELLS TRANSFECTED WITH MUTANTS OF DQB1-ASTERISK-0302

To study epitopes of HLA class II molecules, four mouse monoclonal ant ibodies (mAbs) 13B6, 17F8, 19A1 and 12G6 were made using HLA-DQ8, DP2 and DP4 expressing mouse transfectants for immunization. Three of the mAbs, 13B6, 17F8 and 19A1, bound to all DQ1, 4, 8 or 9 positive B-lymp hoblastoid cell lines (B-LCLs) and transfectants tested, i.e. cells ca rrying the DQB1 genes 0302-3, 0401-2, 0501-3, 0601-4 and 0609 irrespec tive of the accompanying DQA1 gene. These DQB1 genes code for the shar ed amino acids (aa) GVY in position 45-47 of the DQ beta chain. DQ1+48+9 specific (IIB3) and DQ3 specific (IVD12) reference mAbs inhibited binding of all three mAbs. Testing 13B6, 17F8 and 19A1 with cells made using aa substitutions in various positions of DQB10302 indicated in volvement of aa 45 in the epitopes of all three mAbs. The last mAb (12 G6) bound to all B-LCLs and all DP transfected cells. However, only so me DR transfectants and a single DQ transfectant (carrying DQA10201 a nd DQB10202) bound mAb 12G6. This reactivity pattern correlates with a shared sequence of aa (RFDSDVGE) in position 39-46 of DR- and DQ- an d 37-44 of DP beta chains.