In vitro infection of CD4(+) T lymphocytes with HTLV-I generates immortalized cell lines coexpressing lymphoid and myeloid cell markers

The human T cell leukemia/lymphoma virus (HTLV-I) is the etiologic agent of adult T cell leukemia (ATL). CD4(+) lymphocytes are the preferential targe ts of infection, even though other cell types can be infected in vitro by t he virus. Although ATL cells show CD3 and CD4 surface markers, some ATL-der ived cell lines were reported to express also myeloid antigens. In order to analyze possible phenotypic changes induced by HTLV-I after infection of h uman lymphocytes, CD4(+) cells were isolated from peripheral blood of three healthy donors, by separation through immunomagnetic beads. CD4(+) lymphoc ytes were then infected by coculture with irradiated HTLV-I producing MT-2 cells. The phenotypic profile of infected cells was studied by flow cytomet ric analysis using monoclonal antibodies against lymphoid (CD3, CD4, TCR al pha/beta) and myelomonocitic markers (CD13, CD14, CD15, CD33, CD34). The re sults show that HTLV-I immortalized cell lines coexpressed CD13, CD33 and l ymphoid markers. No expression of CD14, CD15 and CD34 was observed. These d ata suggest that the presence of both myeloid and lymphoid phenotype in HTL V-I infected T cells is the results of an induction rather than a selection mechanism.