To investigate the possibility that non-alpha beta T cell-dependent mechanisms can induce systemic autoimmune disease, and to address the roles of alpha beta T cells in murine lupus, we analyzed lupus-prone MRL mice congenitally deficient in alpha beta T cells. Surprisingly, TCR-alpha-/- MRL mice developed several characteristics of human systemic lupus erythematosus, including hypergammaglobulinemia, autoantibodies against DNA and small nuclear ribonucleoproteins, and immune deposits in kidneys. These results, which contrast with past studies concluding that MRL autoimmunity requires CD4+ alpha beta T cells, demonstrate that non-alpha beta T cell-dependent mechanisms are capable of inducing lupus phenomena, and further suggest that MRL disease may consist of both alpha beta T cell-independent and alpha beta T cell-dependent mechanisms.