This work was designed to study the proliferative response of tumor-associated lymphocytes (TAL) from neoplastic effusions against autologous tumor cells and the immunophenotype pattern of TAL from neoplastic effusions and that of PBMC of the same patients. We also compared the serum levels of the cytokines interleukin (IL) 1 beta, 2 and 6, tumor necrosis factor-alpha (TNF alpha) and soluble IL-2 receptor (sIL-2R) with those present in neoplastic effusions of the same patients. Moreover, we examined the ability of TAL and peripheral blood mononuclear cells (PBMC) to produce and release the cytokines and sIL-2R and to express membrane CD25 following their stimulation with phytohemagglutinin (PHA) in vitro. Finally, we compared the cytokines/sIL-2R production and membrane CD25 expression by PHA-stimulated PBMC of the patients with neoplastic effusions with a series of 90 cancer patients without neoplastic effusions and 20 normal healthy subjects. Thirteen neoplastic pleural and eight peritoneal effusions were collected from 11 patients with primary lung cancer, 7 with primary epithelial ovarian cancer, 1 with breast cancer, 1 with pleural mesothelioma, and 1 with pancreatic cancer. The proliferative response of TAL from neoplastic effusions against autologous tumor cells was lower than the response to PHA, IL-2, and anti-CD3, but significant. The percentage distribution of CD3+ and CD8+ lymphocyte subpopulations was higher in peritoneal than in pleural effusions, while the CD16+ subset was higher in pleural than in peritoneal effusions. The percentage distribution of CD16+ was significantly lower in pleural effusions than in PBMC of patients with pleural effusions.(ABSTRACT TRUNCATED AT 250 WORDS)