ALTERATIONS IN T CELLS IN LYMPHOPROLIFERATIVE DISEASE: The overall objective of the proposed study is to test the following hypothesis: The depression of cell-mediated immunity in patients with Hodgkin's disease is related to the dysfunction of thymus-derived (T) lymphocytes. Impairment of T cell function is mediated by antibody which attaches to the surface of T cells and "block" surface receptors which recognize both specific antigens and nonspecific mitogens. The antibody is directed against tumor associated antigens present on T cells in Hodgkin's disease, but not present on T cells of normal controls. A similar depression in cell-mediated immunity in mice bearing certain lymphomas is mediated by antibody directed against tumor associated antigens on the surface of T cells. In order to test the above hypothesis we will examine the T cell surface characteristics and in vitro cell-mediated immune function of peripheral blood lymphocytes (PBL) from patients with Hodgkin's disease, and from mice bearing autochthonous lymphomas. A search for serum factors which alter the T cell surface and function will be carried out.