Immunostimulation of blood monocyte function by RU 41.740 (Biostim) in patients with chronic bronchitis.

RU 41.740 (Biostim), a glycoprotein extract from Klebsiella pneumoniae, which is effective in heightening resistance to experimental infections in animals, was examined with regard to influence on human blood monocyte function in vitro after administration to patients with chronic bronchitis in a randomized, double-blind clinical trial. Twelve patients were given Biostim orally (seven patients received 8 mg daily and five patients received 2 mg daily) while eight patients received placebo. In the Biostim group monocyte phagocytosis increased from 1.4 yeast cells per monocyte before therapy to 3.1 yeast cells per monocyte after 1 month (P less than 0.05) with no further increase after 3 months. Monocyte candidacidal activity increased in the Biostim group from 51% before therapy to 69% after 1 month (P less than 0.05) with a decrease to 57% after 3 months. As expected, placebo had no significant effect on monocyte functions. There was no difference between the improvement in the high dose vs the low dose group. These results suggest that Biostim exerts part of its immunostimulatory property by stimulating blood monocyte antimicrobial function.