 The antibody used in this study is called anti-CD19. It first came from mice that have developed immunity to human lymphoma. This antibody sticks to cancer cells because of a substance on the outside of these cells called CD19. CD19 antibodies have been used to treat people with lymphoma and Leukemia. For this study anti-CD19 has been changed so that instead of floating free in the blood it is now joined to the T cells. When an antibody is joined to a T cell in this way it is called a chimeric receptor. 