In vitro modulation of polymorphonuclear leukocyte functions by a glycoprotein extract from Klebsiella pneumoniae (RU 41740): correction of corticosteroid-induced defects of phagocytosis and adherence.

RU41740 (Biostim®) is a glycoprotein extract from Klebsiella pneumoniae with immunomodulating properties under different conditions. Much evidence indicates that the compound exerts its immunomodulatory function, at least in part, by increasing phagocytic cell functions. In this work the authors have shown that preincubation of normal polymorphonuclear leukocytes (PMNs) with RU41740 improves their capacity to ingest IgG-coated erythrocytes and to adhere to plastic surfaces. To further evaluate the immunostimulatory activity of RU41740, the effect of the drug on human PMNs in which a defect of phagocytosis and adherence had been induced by methylprednisolone (MP) has been studied in vitro. These functional defects could be completely reversed by the addition of RU41740 in the experimental system. Similarly, preincubation of PMNs with RU41740 was able to counteract the defects of ingestion and adherence induced by MP. These results further indicate the immunomodulating properties of RU41740 on phagocytic cells and suggest new therapeutic applications for the compound in selected patients treated with corticosteroids for long periods.