CHARACTERIZATION OF A HTLV-I-INFECTED CELL-LINE DERIVED FROM A PATIENT WITH ADULT T-CELL LEUKEMIA WITH STABLE COEXPRESSION OF CD4 AND CD8

A long-term T-cell line, termed SP+, was developed from a human T-cell leukemia virus type I (HTLV-I)-infected patient with adult T-cell leu kemia that is dependent on exogenous IL-2 for growth. The SP+ expresse s a full complimentation of HTLV-I-specific viral proteins, and contai ns replication competent viral particles. Restriction enzyme digestion followed by Southern blot analysis demonstrated the presence of a sin gle integrated proviral copy and limiting dilution analysis confirmed the clonality of the cell line. Interestingly, phenotypically, the SP cell line is CD2(+), CD3(+) and coexpresses CD4 and CD8, yet lacks TC R alpha beta and TCR tau delta expression. Further ontogenetic charact erization of the SP+ cell line demonstrated the lack of thymic T-cell precursor markers, including absence of cell surface expression of CD1 , intracellular thymic terminal deoxynucleotidyl transferase (TdT) enz yme, as well as message expression for V(D)J recombinase activating ge ne-1 (RAG-1). Furthermore, the SP+ cell did express the message for th e CD3 delta chain. Taken together, these data suggest that the SP+ cel l line resulted from HTLV-I infection of a mature CD4(+)/CDB+ lymphocy te. This cell line can be potentially useful as a model, both for regu lation of cellular functions by HTLV-I and for immunologic functions o f mature dual CD4/CD8 positive T-cells.