[Colony-stimulating factor activity in malignant pleural effusions and its augmentation by local administration of interleukin 2].

The activity of endogenous colony stimulating factor (CSF) in pleural effusions of patients with lung cancer was measured quantitatively by colony-forming bioassay. Before treatment malignant effusions contained various levels of CSF activities. Anti-GM-CSF and anti-M-CSF antibodies neutralized approximately 60% and 70% of CSF activities in malignant effusions, respectively. Significant increase in the CSF activity in malignant effusion was seen during intrapleural injections of recombinant interleukin-2 (IL-2). Thus, in vivo treatment with IL-2 can induce production of endogenous CSF which may be responsible for proliferation and differentiation of mononuclear phagocytes.