In this single-center therapeutic study, we will study the ability of efalizumab to protect remaining beta cells in teenagers and young adults who have been newly diagnosed with type 1 diabetes mellitus. Efalizumab is a monoclonal antibody which prevents the activation of antigen specific T lymphocytes to sites of inflammation. Efalizumab was approved by the FDA in 2003 for the treatment of psoriasis. It has been proven to be safe, well tolerated and effective in targeting T cell mediated disorders like those seen in autoimmunity.