Heterogeneity of the in vitro growth patterns in adult T-cell leukemia cells

Adult T-cell leukemia (ATL) presents heterogeneous clinical features, especially in its clinical course. To clarify the differences in the cell characteristics of these heterogeneous forms, we studied in vitro growth of ATL cells. Nine ATL patients were divided into two groups; 5 acute (group A) and 4 chronic (group B). Although in vitro spontaneous growth was observed only in 3 out of 5 cases in group A, the growth patterns were heterogeneous. When crude interleukin 2 (IL-2) was added to the culture, cells from all the cases in Group A showed marked proliferative responses; these patterns were also heterogeneous. On the other hand, cells in group B displayed no or poor response. The degree of Tac (IL-2 receptor) expression was high in group A but low in group B. These observations suggest that clinical heterogeneity might reflect, at least in part, the cellular heterogeneity in IL-2 responsiveness as seen in vitro.