Tac-positive, HTLV-negative, T helper phenotype chronic lymphocytic leukemia cells

In this report we describe an Italian patient with chronic T cell leukemia whose proliferating cells were mature T lymphocytes with a helper phenotype (T helper phenotype chronic lymphocytic leukemia. or Thp-CLL). Unlike other reported cases of Thp-CLL. fresh leukemic cells from this patient were positive with the anti-Tac monoclonal antibody, which recognizes the receptor for interleukin-2 (IL2). Thus, the phenotype of these cells was similar to that expressed by Japanese patients with adult T cell leukemia (ATL) (OKT3�. OKT4�, OKT8, Tac�). However, the Italian patient had Thp-CLL. not ATL. since his cells. unlike ATL cells, lacked human I cell leukemia virus (HTLV-I)-related T CELL CHRONIC lymphocytic leukemias (TCLL) are a heterogeneous group of lymphopnoliferative disorders characterized by blood accumubation of well-differentiated T lymphocytes. Among T-CLL, adult T cell leukemia (ATL), originally described in Japan,’ � and T helper phenotype (Thp) CLL, reported in Europe and North America,49 are lymphoproliferative disorders of adults. Such disorders are characterized by the expansion of helper phenotype mature T lymphocytes, with frequent splenomegaly, skin lesions, and, usually, an aggressive course. In contrast to Thp-CLL, which is rare but has a worldwide distribution, AlL has been reported to have endemic clusters in southern Japan and in the West Indies.3 Despite the presence of several common featunes, some immunologic,2”0 clinical,” and, especially, epidemiologic3 evidence may indicate that ATL and Thp-CLL are two discrete diseases. In particular, a recent remarkable finding was the discovery of an association between ATL and a new type C retrovirus (the human T cell leukemia virus [HTLV-I]). ATL, but not Thp-CLL, patients have serum antibodies against HTLV-I.’2”3