MODULATION OF HLA CLASS II ANTIGEN EXPRESSION BY TRANSFECTION OF SENSE AND ANTISENSE DRa cDNA BY VINCENT LOTTEAU,` JOHN SANDS,' LUC TEYTON,~ PASCALE TURMEL," DOMINIQUE CHARRON,t AND JACK L. STROMINGER'

The HLA class II molecules of the human MHC are cell surface glycoproteins that play a critical role in the immune response regulation . At least three HLAclass II isotypes have been described (HLA-DR, -DQ, and -DP), each composed of an a and a ß chain (1) . In addition to conventional HLA class II molecules, the existence of hybrid molecules formed by transcomplementation (hybrid HLA-DQ) and interisotypic pairing (HLA-DRa-DQß) has been previously reported (2, 3) . In the context of our understanding of immune regulation and HLA class II-linked autoimmune diseases, it is of particular interest to modify the class II phenotype by creating or suppressing individual specificities. To modulate the expression of class II molecules, human EBVtransformed B cell lines were transfected with sense and antisense DRa cDNA. We show that quantitative variation of the DRa chain leads to de novo expression or extinction of the DRa-DQß dimer.