In vitro and in vivo effects produced by the immunomodulating agent RU 41740 on human polymorphonuclear leukocytes in the elderly

The activity of RU 41740, a glycoprotein extract from Klebsiella pneumoniae has been investigated on some polymorphonuclear (PMN) functions. Chemotaxis, random migration and oxidative metabolism (assessed by chemiluminescence, O2 consumption and O2- generation) were studied in parallel. PMN were collected from adult and aged human volunteers. Experiments were performed either in vitro or in vivo in a double blind placebo assay. In both PMN populations RU 41740 enhanced oxidative metabolism either in in vivo or in vitro experiments. However, a higher and dose-related activity was observed on PMN collected from the younger subjects whereas maximal effective concentration was reached earlier with PMN collected from aged subjects. RU 41740 did not modify random migration but inhibited chemotaxis of PMN collected from the younger population in a dose-related manner. These data corroborated previous results observed on PMN collected from various animal species and suggested an interaction of RU 41740 on PMN membrane. Moreover drug-induced macrophage and lymphocyte stimulation might also explain, at least in part, the in vivo effects described in this study. Thus RU 41740 could partly account for the protective effects exerted against bacterial and fungal infections through its activity on PMN functions.