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The leukaemic cells of 11 patients with Japanese adult T-cell leukaemia (ATL) were characterized in terms of phenotype employing various monoclonal antibodies against T-cell surface antigens. The leukaemic cells of all ATL patients except patient no. 11 displayed the phenotype OKT4+/OKT8-. However, the % of OKT3+cells varied from 3 to 98. In 1 case, cells with phenotype OKT4+/OKT8+, which is characteristic of T-cells at an early stage of differentiation, were found. These results suggest that some ATL cells may be in an immature differentiation stage. Among the 11 patients, 2 with unusual ATL cell phenotypes (1 case with OKT3-cells and 1 case with Ia+/EAC+cells) showed spontaneous regression of leukaemic cells. Characterization of leukaemic cells from a larger number of ATL patients may demonstrate a significant relationship between cell phenotype and prognosis.

Six patients with lymphoproliferative disorder of large granular lymphocytes (LDGL) were studied for chromosomal abnormalities. When the patients were divided into two groups depending on the expression of a mature antigen of T cell lineage, CD3, two with CD3+ phenotype had a stable disease, whereas three of the four patients with CD3- phenotype had marked hepatosplenomegaly and a highly aggressive disease. Chromosomal abnormalities were detected in four of six patients, indicating a clonal proliferation of large granular lymphocytes in individual patients. In particular, chromosomal abnormalities were found in three of the four patients with CD3- LDGL, all of which had a germ-line configuration of the T cell receptor beta-chain gene. Thus, the chromosomal abnormalities provide definitive evidence for the clonal origin of the expanded cells in the CD3- LDGL.

A case of chronic leukemia is reported. Malignant cells had the morphology of lymphocytes and an affinity for skin. Cytochemically, they were peroxidase negative, and NaF-resistant alpha-naphthyl esterase positive. The peripheral mononuclear cells formed E-rosettes and reacted with Leu 1 and OKM1. They were unreactive with OKT3, OKT4, OKT6, OKT8, and OKIa1. The cells did not possess surface IG, C3b receptors, or IgG Fc receptors (EAIgG). They responded weakly to phytohemagglutinin, and did not respond to concanavalin A. The cells did not adhere to Petri dishes or phagocytose latex beads. It is concluded that it was a case of OKT3-, OKM1+, EAIgG- T-cell chronic lymphocytic leukemia. This suggests that OKT3 does not recognize all peripheral T-cells, and that OKM1 is not specific for the monocyte-myeloid lineage. These cells may be useful in the characterization of E+, OKM1+ subset of peripheral mononuclear cells.

The morphologic features, phenotype, and functions of OKM1+ leukemic T-cells were studied. The leukemic T-cells in two patients with chronic lymphocytic leukemia (CLL) had specific features of large granular lymphocytes (LGL), and those in two patients with acute lymphocytic leukemia (ALL) had L2 morphologic characteristics. The phenotype of the leukemic cells from one patient with CLL was OKM1+, ER+, OKT3+, OKT4+, OKT8-, OKIa1-, IgGFc receptor (EA gamma)+, Leu-7+, Leu-11b+, and anti-Tac-. The cells had antibody-dependent cell-mediated cytotoxicity (ADCC), but no natural killer (NK) activity. They had a definitive helper effect on pokeweed mitogen-induced normal B-cell differentiation. The leukemic cells from the other patient with CLL were Leu-7-, and Leu-11b-, and lacked both ADCC and NK activity. The leukemic cells in the two patients with ALL were ER+, OKM1+, Leu-7-, and Leu-11-, and did not have any cytotoxicity. One was EA gamma +, and the other was EA gamma -. These findings suggest that OKM1+ leukemic T-cells consist of at least two subgroups: (1) T-cells with the morphologic features of LGL; and (2) those with a lymphoblastic morphologic type. In either case, the phenotype is novel and suggests the emergence of a small, distinct lymphocyte subset.