Fig. 1. IL-9 inhibits the growth of murine T lymphomas transfected with the human IL-9R. Lymphoma cells were stably transfected with the hIL-9R inserted into the pEF-BOS-puro plasmid (6) . Transfected cell populations were grown in the presence of murine ({square}) or human ({blacklozenge}) IL-9 (1000 cells/well). After 4 days, cell numbers were evaluated by measuring hexosaminidase levels (6) . Similar results were obtained by measuring thymidine incorporation.