Potentiation of Antitumor Activity by Antibody Drugs and Mushroom-Derived β-Glucans in Natural Killer Cell-Mediated Tumoricidal Activities against Non-Hodgkin's B-Cell Lymphoma.

β-glucans are polysaccharides that activate innate immunity. We herein investigated whether P-glucans promote the immunological effects of antibody drugs against malignant tumor cells using human peripheral blood mononuclear cells (PBMCs). Rituximab bound to CD20-specific lymphoma and exhibited cytotoxic activity in the presence of human mononuclear cells, but not neutrophils. The addition of Sparassis crispa (cauliflower mushroom)-derived β-glucan (SCG) and granulocyte macrophage colony-stimulating factor (GM-CSF) to co-cultures of PBMCs and Raji lymphoma cells further promoted antibody-dependent cell-mediated cytotoxicity (ADCC). The GM-CSF treatment increased β-glucan receptor expression on adherent cells in PBMCs. A co-stimulation with GM-CSF and SCG of PBMCs induced an increase in the number of spreading cells and the activation of natural killer (NK) cells. The enhancement in ADCC was abolished by the removal of NK cells, indicating that SCG and GM-CSF increased ADCC against lymphoma by activating β-glucan receptor-expressing cells in PBMCs and enhancing NK cell activity. The synergistic mechanisms of action of mushroom-derived β-glucans and biopharmaceuticals, including recombinant cytokines and antibodies, in the treatment of malignant tumor cells provide important insights into the clinical efficacy of β-glucans from mushrooms.