Bubier, Jason A.

Abstract Systemic lupus erythematosus (SLE) inflicts damage via autoantibody complexes that result in multiorgan damage and renal failure. The BXSB.Yaa mouse is a well-established model of SLE. We show that genetic disruption of multiple components of the MHC I axis greatly accelerates autoimmune disease in this model. Mice lacking both CD8 and IL15 succumb to SLE-like disease earliest (mean age 14 wks), implying a protective role for CD8 T cells and potentially natural killer cells dependent on IL15. BXSB.Yaa mice develop an expanded population of CD8 T cells with increased expression of both CD122 and IL15Rα, which we propose is due to increased expression of IL15R on these cells. Neither Foxp3 nor CD25 are elevated, and IL10 deficient BXSB.Yaa mice fail to show accelerated disease. However, lytic function appears significant as BXSB.Yaa mice deficient in perforin show decreased survival. TCR analysis failed to suggest a biased CD8 T cell repertoire, suggesting that the cellular targets of suppression are not antigenically discrete. Overall, the results suggest the existence of potent MHC I-dependent suppressor cell population(s) that normally protect BXSB.Yaa mice from an even more aggressive form of SLE-like disease. Moreover, the results support a model in which suppression is unlikely to be mediated by cytokine regulation but instead by lytic mechanisms. Harnessing this inherent regulatory cell population could provide a novel strategy to treat SLE and related syndromes.