Immunoglobulin production stimulating and inhibiting factors derived from human lung adenocarcinoma PC-8 cells

Addition of a 3 M KCl extract of a human lung adenocarcinoma PC-8 cells to the culture media of lymphocytes, which were isolated from normal donors and from lung or breast cancer patients, elevated immunoglobulin (Ig) production by 3–5 times in the presence of pokeweed mitogen. However, addition of higher concentration of the extract inhibited Ig production and proliferation of lymphocytes. The Ig production stimulating factor (IPSF) was separated from the inhibiting factor, using 50% ammonium sulfate precipitation. Upon chromatofocusing, IPSF activity was detected mainly in the pH 4.5 fraction but minor activity was also detected in other pH fractions. IPSF also enhanced Ig production of a B-lymphoblastoid cell line transformed by Epstein-Barr virus and a human-human hybridoma, by more than 2-fold. This suggests that IPSF interacts with B-lymphocytes directly to enhance their Ig production. IPSF activity was also detected diversely in human lung squamous carcinoma QG56, human B-lymphoblastoid HO-323, and a T cell line CEM.