CTLA4-Ig (Abatacept) inhibits a crucial stimulatory pathway in the activation of T cells. By this mechanism, the drug is thought to arrest or slow the T cell mediated autoimmune destruction of beta-cells and preserve their function. At the time of clinical onset of T1DM, a significant amount of insulin producing beta cells are destroyed, but as many as 10-20% are still capable of insulin production. By using CTLA4-Ig close to the onset of T1DM, we hope to arrest or slow down the autoimmune destruction of these beta-cells and extend the endogenous insulin production. CTLA4-Ig regulates T cell function but does not deplete T cells. Therefore, its safety profile appears to be better than other immunosuppressive agents.