Spontaneous Proliferation of H2M-/- CD4 T Cells Results in Unusual Acute Hepatocellular Necrosis

Naı̈ve CD4 T cells are triggered to undergo spontaneous proliferation, a proliferative response induced in response to homeostatic stimulation, when exposed to severe lymphopenic environments. They spontaneously acquire proinflamma-tory effector phenotypes, playing a major role in inducing chronic inflammation in the intestine that is believed to be induced by T cell recognition of commensal antigens. While the antigens inducing the T cell responses and inflammation are being extensively investigated, the role of clonality of T cells involved in this process remains poorly understood. In this study, we utilized naı̈ve CD4 T cells isolated from B6 H2M2/2 mice, in which MHCII molecules are complexed with a single CLIP molecule, and examined spontaneous proliferation and intestinal inflammation of CD4 T cells expressing limited T cell receptor repertoire diversity. We found that H2M2/2 CD4 T cells undergo robust spontaneous proliferation, differentiate into IFNc-producing Th1 type effector cells, and, most unexpectedly, induce severe acute hepatocellular necrosis. T cell interaction with MHCII molecule on cells of hematopoietic origin was essential to induce the pathology. Interestingly, B cells are fully capable of preventing necrotic inflammation via IL-10-independent and B7-H1-dependent mechanism. This could be a useful animal model to examine T cell-mediated liver inflammation and B cell-mediated immune regulation