Abstract
Non-adherent effusion cells (EC), mostly lymphocytes, were isolated from the pleural effusions of 8 patients with malignant and 7 patients with benign disease. C. parvum [Propionibacterium acnes] (Cp) induced increased 3H-thymidine (methyl-3H-TdR) incorporation in EC cultures, but the response was lower than that usually found with autologous or allogeneic normal human blood lymphocytes. Experiments with highly purified effusion lymphocytes indicated that the response to Cp was influenced by the presence of adherent cells, probably macrophages. Normal human monocytes incubated in vitro with supernatants of unstimulated EC cultures expressed slightly increased ability to suppress methyl-3H-TdR-incorporation in a human tumor cell line. Supernatants of Cp-stimulated EC induced a further increase in monocyte-mediated cytostatic activity. Cell-free effusion fluids from 8 patients were largely inactive when tested for induction of monocyte-mediated cytostatic activity in the same system, and the effusion fluid reduced monocyte methyl-3H-TdR-incorporation in vitro. Cp seems to be able to induce DNA-synthesis and release of mononuclear phagocyte-activating lymphokines in human effusion lymphocytes.