Protodyne: an immunostimulatory protein component, prepared from gram-positive Bacillus subtilis.

A protein component derived from bacterial protoplasm, called Protodyne, increases the non-specific resistance to infections by bacteria and viruses. Here we show that Protodyne can be prepared not only from Gram-negative bacteria, but also from Gram-positive bacilli. Several preparations of Protodyne, prepared from Bacillus subtilis by phenol extraction or by ammonium sulfate precipitation, were evaluated for immunomodulatory activities in a variety of assays. Protodyne had a marked mitogenic activity on mouse spleen cells; it was a potent inducer of tumor necrosis factor (TNF) and stimulated production of interleukin-1 (IL-1) in human peripheral blood mononuclear cells; it increased the capacity of activated macrophages to undergo a respiratory burst, to produce intracellular killing of leishmanial parasite and extracellular lysis of mastocytoma cells; it also stimulated phagocytosis of latex particles, and prolonged survival of immunosuppressed mice infected with Pseudomonas aeruginosa. These activities were not inhibited by polymyxin B, indicating that the activity of Protodyne is not the result of contamination with exogenous lipopolysaccharide. It appears that Protodyne exerts its many immunomodulatory actions by inducing the release of soluble mediators, including TNF and IL-1.