Ben‐Nun, Avraham

Abstract A20.2J B lymphoma cells have been co-transfected with the A alpha b, A beta b or with the A alpha b, A beta bm12 and neomycin resistance genes. The transfected cell lines constitutively express the I-Ab or I-Abm12 class II molecules at a level comparable with that of the endogenous I-Ad antigen. The I-Ab antigens expressed on three independently transfected B cell clones (A20.Ab.1, A20.Ab.2, and A20.Ab.3) are serologically and functionally indistinguishable from the I-Ab molecules expressed by control H-2bxd B hybridoma cells (LB cells). These transfected cell lines were potent I region-restricted antigen-presenting cells to a large panel of antigen-specific, autoreactive and alloreactive T cell hybridomas, as well as normal T cell clones. There were not significant differences in the efficiency of antigen presentation by the Ia molecules encoded by the transfected, as compared with the endogenous, I-A genes. The expression of a functional I-Ab antigen on the surface of cells transfected with A beta bm12 and A alpha b genes is consistent with previous work that implicated the A beta-chain alone in the bm 12 mutation. Furthermore, because the transfected A20.Ab and A20.Abm12 cells display the serologic and functional properties of normal spleen cells from the wild-type and mutant mouse strains, respectively, it is clear that class II genes do not undergo unexpected and unpredictable alterations after transfection in this system. This system permits us to investigate the structural requirements for interactions between class II major histocompatibility complex antigens, a foreign antigen, and the T cell receptor by in vitro site-directed mutagenesis coupled with DNA-mediated gene transfer.

Abstract The susceptibility to multiple sclerosis (MS), a chronic neurological autoimmune disease that primarily targets CNS myelin, has long been associated with HLA class-II genes. Although several other HLA and non-HLA disease predisposing alleles have been identified, alleles of the HLA-DR15 haplotype (DRB1*1501, DRB5*0101, and DQB1*0602) remain the strongest susceptibility factor. Many studies have suggested that the HLA-DRB1*1501 allele determines MS-associated susceptibility. However, due to strong linkage disequilibrium within the HLA class II region, it has been difficult to unequivocally determine the relative roles of the DRB1*1501 and DQB1*0602 products. In this study we use HLA class-II transgenic mice to illuminate the relative contributions of the DRB1*1501 and DQB1*0602 alleles or their combination to susceptibility toward a new “humanized” MS-like disease induced by myelin-associated oligodendrocytic basic protein (MOBP). Although many immunological studies have focused overwhelmingly on the role of the HLA-DRB1*1501 product in MS, we show that HLA-DRB1*1501 transgenics are refractory to MOBP disease induction, whereas the HLA-DQB1*0602 transgenics are susceptible via T cells reactive against MOBP15–36 and MOBP55–77 encephalitogenic epitopes. Although both transgenics react against these epitopes, the MOBP15–36- and MOBP55–77-reactive T cells are of Th2-type in HLA-DRB1*1501 transgenics and are pathogenic Th1/Th17 cells in the HLA-DQB1*0602 transgenic mice. This new humanized model of MS further implicates autoimmunity against MOBP in MS pathogenesis, provides the first evidence of pathogenic HLA-DQ-associated anti-myelin autoimmunity, and is the first to offer a rationale for HLA-DQB1*0602 association with MS. These findings have important bearing on the candidacy of the DQB1*0602 allele as a genetic risk factor for MS.