Transformation of different phenotypic types of human bone marrow T-lymphocytes by HTLV-1

Fresh bone marrow mononuclear leukocytes were used as a target for infection by human T-cell leukemia-lymphoma virus subgroup 1 (HTLV-1) by co-cultivation with virus-positive cell lines. The lines were established from T-cell leukemia-lymphoma patients or HTLV-1-transformed human umbilical cord-blood T cells. Clumps of transformed cells became visible by 2-3 weeks after infection and developed at a high frequency (greater than 90%) in the bone marrow samples used. Stimulation of target cells with lymphocyte mitogens facilitated this process but was not absolutely required. Unlike fresh or cultured cells from HTLV-1-positive adult leukemia-lymphoma patients and HTLV-1-transformed cord-blood T cells, which usually have an OKT 4/leu 3a surface phenotype, the transformed bone marrow cells frequently fell into one of three categories based on their reactivity with cell-specific monoclonal antibodies. These included populations of cells that were predominantly; (1) OKT 4/leu 3a-positive, (2) OKT 8/leu 2a-positive, and (3) cells expressing neither phenotype. Fresh bone marrow provided a rapid and efficient system for the assessment of HTLV-1 infection. The type of bone marrow cells transformed in vitro suggests that HTLV-1 can infect several subsets of T lymphocytes, possibly including immature cells or that these cells can undergo phenotypic modulation.