Exogenous nitric oxide modulates cytokine production in human leukocytes.

Exogenous nitric oxide was found to modify the pattern of cytokine secretion from human leukocytes, with similar outcome in 11 different healthy blood donors. Peripheral blood mononuclear cells (PBMC) were stimulated with phytohaemagglutinin (PHA) in the presence of increasing amounts of the NO donor S-nitroso-N-acetyl-penicillamine (SNAP). The NO donor dose-dependently enhanced IL-4 secretion into the supernatant (p<0.01). In contrast, IFNgamma production was not affected while IL-10 levels were slightly decreased. Comparable changes were observed when analysing cytokine mRNA levels by semiquantitative RT-PCR. The differential effect of the NO donor on IL-4 versus IL-10 and IFNgamma gene expression suggests an immunomodulatory potential of NO, which may serve to limit inflammatory responses.