Interleukin 10 suppresses phagocytic and antihyphal activities of human neutrophils.

We investigated the effects of human interleukin 10 (IL-10) on the antibacterial and antifungal activities of human neutrophils (PMNs) against Staphylococcus aureus and Candida albicans. Incubation of PMNs from healthy volunteers with 20-100 ng/ml of IL-10 at 37 degrees C for 1 h suppressed phagocytosis of serum-opsonized S. aureus (P=0.02) and blastoconidia of C. albicans (P<0.01). In contrast, 2-100 ng/ml of IL-10 had no effect on superoxide anion production upon stimulation with phorbol myristate acetate, N-formylmethionyl leucyl phenylalanine, C. albicans blastoconidia or pseudohyphae; neither did it significantly affect conidiocidal or bactericidal activities of PMNs. However, 20-100 ng/ml of IL-10 significantly decreased PMN-induced damage of C. albicans pseudohyphae (P=0.008). The suppression of phagocytic activity of PMNs against S. aureus and blastoconidia of C. albicans as well as the impairment of PMN-induced hyphal damage may have important implications for understanding the immunosuppressive profile of IL-10 in clinical usage.