Influence of porcine natural modified surfactant on chemotaxis and oxidative metabolism of polymorpho-nuclear leukocytes

Surfactant has been shown to influence a variety of immune functions. However, for in vitro studies most investigators used a single surfactant concentration often far below what has to be expected in bronchoalveolar fluid following surfactant replacement therapy. We studied the chemotactic activity and the oxygen metabolite release of human polymorphonuclear leukocytes (PMN) following incubation with Curosurf®, a porcine modified natural surfactant preparation, at concentrations ranging from 1 to 16 mg/ml. In the presence of 1% bovine serum albumin, surfactant at 1 and 4 mg/ml enhanced anaphylatoxin C5a-related chemotaxis, whereas a higher dose of 16 mg/ml was inhibitory. Furthermore, Curosurf® itself demonstrated a concentration-dependent chemotactic effect. Oxygen metabolite release, as measured by nitroblue tetrazolium reduction, was significantly diminished at surfactant concentrations of 8 and 16 mg/ml. This effect was most pronounced when group B streptococci at concentrations 5 × 10⁹ CFU/ml were applied for PMN stimulation. We conclude that the effects of surfactant on PMN immune functions are not only concentration-dependent but also influenced by the degree of PMN stimulation.