INDUCIBLE NITRIC-OXIDE SYNTHASE EXPRESSION IN PORCINE IMMUNE CELLS

Porcine immune cells were examined for the ability to produce inducibl e nitric oxide synthase following in vitro or in vivo stimulation. Enz yme activity and product formation were not detected following stimula tion of porcine peripheral blood mononuclear cells (PBMC), splenocytes , or alveolar macrophages with a combination of ConA and lipopolysacch aride (LPS) or recombinant porcine interferon gamma and LPS. in vitro engulfment of Haemophilus parasuis by macrophages also failed to induc e inducible nitric oxide synthase (iNOS) activity or nitrite formation . Swine Herpes Virus infection led to a small but significant increase in level of nitrite detected in lung lavage fluid, whereas the infect ion of pigs with Porcine Respiratory and Reproductive Syndrome Virus d id not alter the lavage fluid nitrite levels. iNOS mRNA was detected i n both stimulated and unstimulated porcine immune cells and in macroph ages from both control and infected animals suggesting that it is cons titutively expressed with little or no upregulation following cellular stimulation. The results presented in this paper indicate that the re active nitrogen intermediate pathway is not an vital innate immune res ponse in the pig. (C) 1998 Elsevier Science B.V.