Augmentation of human blood monocyte microbicidal activity by RU 41740, a glycoprotein extract from Klebsiella pneumoniae.

Non-specific activation of host defences may have a significant impact on the outcome of infections in the immunocompromized patient. RU 41740, a glycoprotein extract from Klebsiella pneumoniae, effective in increasing resistance to experimental infections in animals, has been examined in vitro for its effect on human blood monocyte locomotion, phagocytosis, killing of Candida albicans, and release of superoxide anion. RU 41740 had no chemo-attractant activity nor any effect on monocyte chemotactic and phagocytic function. Candidacidal capacity and superoxide anion production by monocytes were significantly enhanced after preincubation with RU 41740 greater than 1.0 microgram/ml. The effect was dose- and time-dependent and was not influenced by the presence of lymphocytes or their culture supernatants. This suggests a direct interaction with monocytes as the mechanism of action of the extract.