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We reported a peculiar case with T cell leukemia. The patient was a 34- year-old woman showing extensive splenomegaly and marked leukemic cell proliferation and running a rapid fatal clinical course. The leukemic cells were morphologically ordinary lymphocytes showing suppressor/cytotoxic(s/c) T cell phenotypes and containing S-100b protein. Southern blot analysis revealed rearrangement of the beta chain genes of the T cell receptor (TcR) of the leukemic cells. Because these phenotypic and morphologic features were identical with those of S-100 beta+T lymphocytes (S-100 beta +TL) in normal human peripheral blood, we regarded this case as S-100 beta +T cell leukemia. We discussed clinicopathological features of S-100 beta +T cell leukemia/lymphoma by assessing similar cases reported so far. S-100 beta +T cell leukemia/lymphoma is a new type of s/c T lymphocytic leukemia/lymphoma with aggressive features.

We studied the mode of natural transmission of human T-cell leukemia virus type I (HTLV-I) in rabbits. Four virus-infected rabbits (2 males and 2 females) were individually mated with 4 noninfected rabbits. Two virus-infected females mated with noninfected males gave birth to 7 offspring, and 2 noninfected females mated with infected males delivered 5 offspring. Four of the seven offspring born to the virus- infected mothers seroconverted for HTLV-I when aged 6 to 13 weeks with antibody titers of 1:40 to 1:160. None of the five offspring born to the noninfected mothers became seropositive during the observation period of 6 months, however. Peripheral lymphocytes were cultured with T cell growth factor, and HTLV-I-carrying lymphoid cell lines were established from the four seroconverted rabbits. All four cell lines were of T cells positive for Ia antigens. In addition, none of five newborn rabbits killed immediately after birth to a virus-infected rabbit was infected with HTLV-I. These findings provide an experimental support for the milkborne transmission of HTLV-I from mother to child in humans and indicate that the virus is tropic for T cells in rabbits as well.

A myeloid cell line, designated PL-21, was established from the peripheral blood of a patient with acute promyelocytic leukemia. The PL- 21 cell line grew in single-cell suspension, with a doubling time of 48– 64 hr, and consisted of promyelocytes with fine immature nuclei and prominent azurophilic granules in the cytoplasm. PL-21 cells were positive for peroxidase, naphthol AS-D chloroacetate esterase, and Sudan Black B staining. Under the usual culture conditions, a small proportion of these cells differentiated into mature granulocytes, and this differentiation was enhanced by the addition of dimethyl sulfoxide in the culture medium. PL-21 cells had receptors for the Fc portion of IgG and complement, intracytoplasmic lysozyme and phagocytic activity, but lacked Epstein-Barr virus-associated nuclear antigen. Chromosome analysis of this cell line revealed a human male polyploid karyotype with 13q+ and double minute chromosomes. This new myeloid cell line may provide useful material for the study of proliferation and differentiation of human leukemia cells.

The characteristics of human S-100 beta-positive T lymphocytes (S-100 beta+ T cells) and their fluctuation in peripheral blood under normal and various pathologic conditions were investigated. S-100 beta+ T cells were small lymphocytes with no particular subcellular structures and showed a proliferative response to mitogens. They were present mainly in peripheral blood under normal conditions but accumulated in T zones of lymph nodes with nonspecific T-zone hyperplasia, where numerous interdigitating reticulum cells existed. In healthy adults approximately 1% to 4% (mean 3.4%) of peripheral blood mononuclear cells were S-100 beta+ T cells. The proportion of S-100 beta+ T cells in peripheral blood tended to significantly decrease (less than 0.5%) in patients with neoplastic diseases; this tendency was apparently related to tumor progression.