Specifying the autoantibody-inducing CD4 T cell causing systemic lupus erythematosus out of PD-1+CD45RBlo122lo CD4 subpopulation using mass spectrometry (BA11P.135)

Abstract

Abstract Objective: We have shown that repeated immunization of mice with antigen reproducibly led to development of experimental systemic lupus erythematosus (SLE), where a novel T cell type which we term an autoantibody-inducing CD4 T (aiCD4 T) cell was generated via TCR revision at periphery. The aiCD4 T cell induces varieties of autoantibodies and also helps full maturation of CTL to induce lupus tissue injuries. We have previously identified that aiCD4 T cell belongs to PD1+CD45RBlo122lo CD4 T subpopulation. Here we tried to further specify the aiCD4 T cell by membrane surface markers. Methods: BALB/c mice were repeatedly 12x immunized with OVA. To isolate aiCD4 T cell, we extracted cytoplasmic and membrane fractions of PD1+CD45RBlo122lo CD4 T subpopulation. They were electrophoresed and protein fractions unique to the PD1+CD45RBlo122lo CD4 T subpopulation were identified thru mass spectrometry. Results: Candidate membrane markers as suggested by mass spectrometry were DNA topoisomerase 2-beta (181 kDa), DOCK 8 (238 kDa), VWA5A (87 kDa), STAT5b (89 kDa), epidermal growth factor receptor substrate 15-like 1 (99 kDa) and FLAP (18 kDa) for aiCD4 T cell, among which we found that DOCK 8 was significantly increased in the membrane fraction of PD1+CD45RBlo122lo CD4 T subpopulation. Conclusion: We identified DOCK 8 as a possible candidate membrane marker characterizing the aiCD4 T cell as found within PD-1+CD45RBlo122lo CD4 T subpopulation.