Abstract
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 (>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.