The objectives of this research are directed at characterizing lymphoid cells involving in human lymphoproliferative neoplasia, particularly acute and chronic lymphocytic leukemia and lymphoma. Recently established permanent lymphoid cell lines (MOLT number 1,2,3,4 and RPMI number 8402) from patients with acute lymphoblastic leukemia will be further characterized for their characteristics representing thymus- derived lymphocytes. Heterologous antisera against these T-cells are also used for identifying various leukemia-lymphoma cells. Cytotoxic test and immunofluorescent test with these antisera will be used for the study. Attempts will be made in these tests to identify the human leukemia antigens.