In vitro Augmentation of Natural Killer Cell Activity and Production of Interferon‐α/β and ‐γ with Deoxyribonucleic Acid Fraction from Mycobacterium bovis BCG

A nucleic acid‐rich fraction extracted and purified from BCG (MY‐1) augmented natural killer (NK) cell activity of mouse spleen cells in vitro, and produced factor(s) which showed anti‐viral activity and rendered normal macrophages cytotoxic towards tumor cells. These cellular responses were induced by the MY‐1 digested preliminarily with RNase, but not by the MY‐1 digested with DNase, indicating that DNA contained in MY‐1 was essential for the responses. The function of the factor to activate macrophages was destroyed by treatment with a small amount of anti‐interferon (IFN)‐γ antiserum or under acidic conditions (pH 2), but not by treatment with anti‐IFN‐α/β antiserum, while the anti‐viral activity was destroyed almost completely by treatment with anti‐IFN‐α/β antiserum. It appears that DNA from BCG stimulated mouse spleen cells in vitro, resulting in augmentation of NK activity and production of IFN‐α/β and ‐γ.