Phenotypical heterogeneity of Japanese adult T-cell leukaemia

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.