Adult T-cell leukemia.

Adult T-cell leukemia (ATL) is a leukemia caused by a monoclonal expansion of HTLV-I-infected T-cells expressing a CD4 antigen. The clinical features of ATL include lymphadenopathy, hepatosplenomegaly, frequent skin lesions, hypercalcemia and a rapidly fatal course. The cell surface phenotype, cytogenetics and functions of leukemic cells are described in association with various clinical manifestations and HTLV-I infection. Leukemic cells constitutively express the p55 (Tac antigen) subunit of the interleukin-2 (IL-2) receptor. Its association with the function of HTLV-I gene products and its possible role in the leukemogenesis of ATL are discussed. Finally, the potential of some therapeutic agents which may selectively eliminate the Tac-expressing leukemic cells in vitro are described, and these may provide an improvement over currently ineffective combination chemotherapy.