Interleukin‐2 production by primary adult T cell leukemia tumor cells is macrophage dependent

We have investigated the cellular requirements for IL‐2 production by autocrine proliferating tumor cells from four patients with adult T cell leukemia (ATL). Cultures of these ATL cells both produced endogenous IL‐2 protein in the absence of added mitogen and proliferated at higher levels when exogenous recombinant IL‐2 was added. Depletion of macrophages in the tumor cell cultures resulted in a sharp decline in tumor cell IL‐2 production, while re‐addition of macrophages reconstituted this response. Macrophage‐derived factors including IL‐6 and IL‐1 also reconstituted IL‐2 production in these macrophage depleted cultures. These results raise the possibility that macrophages may play a central role in HTLV‐I mediated immortalization of T cells. © 1992 Wiley‐Liss, Inc.