Cellular interactions in hemopoiesis.

: The role of immunocompetent cells in hemopoiesis remains controversial. We used an autologous system in which activated peripheral blood mononuclear cells (LAK) and interleukin-2 (IL-2) are administered to patients with cancer. We found little change in the numbers of circulating erythroid progenitors. Cocultures of these progenitors with LAK or supernatants lead to a decrease in the numbers of detectable burst forming units-erythroid (BFU-E) in culture. However, using an assay for burst promoting activity (BPA) we noted production of this hemopoietin by these LAK cells. We could not detect circulating levels of gamma interferon (IF). Variable levels were found in the LAK supernatants. We could not detect circulating eosinophil progenitors (CFU-Eo), but we did find evidence of production of a colony stimulating factor (CSF), which gave rise to a high number of eosinophil colonies in cultures of bone marrow. These results suggest that administration of LAK/IL-2 has potent effects on hemopoiesis and that these effects may emphasize the anemia and eosinophilia seen in patients receiving this therapy.