Cognate interaction plays a key role in the surveillance of autoreactive B cells in induced mixed bone marrow chimerism in BXSB lupus mice.

The effects of bone marrow transplantation (BMT) as a treatment for and/or preventive measure against autoimmune diseases in mice were investigated extensively. The reconstitution of the hematopoietic system with a mixture of autologous and heterologous bone marrow cells was reported to suppress the development of autoimmune diseases. However, the pathological mechanism through which mixed chimerism results in the suppression of disease development is still unknown. We have previously reported that the induction of fully major histocompatibility complex (MHC)-mismatched allogeneic mixed chimerism can prevent the disease development in BXSB mice. Interestingly, serum anti-dsDNA IgM antibody (anti-DNA IgM) levels were not significantly decreased in these chimeric mice, though other symptoms of autoimmune disease were ameliorated. In this study, we showed that self-reactive anti-DNA IgM production was mainly attributable to genetically normal B cells from the donor rather than genetically deficient B cells from the host. Host-type B cells responded normally to foreign antigens and produced the appropriate antibodies. BMT from fully MHC-matched or haplo-identical donors could suppress the production of anti-DNA antibodies. Our present study suggests the existence of a surveillance system dependent on the recognition of MHC molecules on B cells.