AbstractThe in vitro effects of lentinan on natural killer (NK), antibody-dependent cell-mediated cytotoxicity (ADCC), lectin-dependent cell-mediated cytotoxicity (LDCC) and mitogen-induced blast transformation were studied in patients with solid tumors and chroyic lymphocytic leukemia (CLL). NK activity was measured against Cr-labelled K-562 targets, ADCC against antibody-coated chicken red cells. LDCC and natural cell-mediated cytotoxicity (NCMC) was assessed using3H-thymidine prelabelled HEp-2 targets. Mitogen (PHA-and Con A-) induced blast transformation was measured by thymidine incorporation.Blastogenesis and LDCC was not influenced by lentinan. 1μg/ml lentinan increased NCMC of tumor-bearing subjects. The most prominent enhancement of NK and ADCC activity was seen in CLL patients, where a dose-related increase was seen (from 0.01 to 1μg/ml).