ASSESSMENT OF BOVINE MONONUCLEAR PHAGOCYTES AND NEUTROPHILS FOR INDUCED L-ARGININE-DEPENDENT NITRIC-OXIDE PRODUCTION

Microbicidal activity of reactive oxygen intermediates and reactive ni trogen intermediates has been described from both murine and human cyt okine activated macrophages. An L-arginine-dependent pathway of nitric oxide generation has recently been described from bovine bone marrow- derived and monocyte-derived macrophages in response to a phagocytic s timulus. We have investigated the induction and release of both reacti ve oxygen intermediates and reactive nitrogen intermediates from bovin e neutrophils, and blood and spleen mononuclear phagocytes in response to either a phagocytic or cytokine stimulus. Mononuclear phagocytes w ere poor producers of hydrogen peroxide (a measure of reactive oxygen intermediate production) under conditions that readily caused release by neutrophils. In contrast, nitrite, as a measure of nitric oxide pro duction, could not be induced from neutrophils under any stimulation c onditions, while mononuclear phagocytes responded to both a phagocytic stimulus and cytokines with the induction of nitric oxide synthase me ssage and production of nitric oxide. There appeared to be two populat ions of monocytes that differed both in their adherent characteristics and their level of cytokine-induced nitric oxide production. Both pop ulations stained with a single monoclonal antibody. However, the popul ation that had not adhered to plastic within 3 h responded to cytokine stimulation, producing up to 3 times more nitric oxide on a per cell basis than the readily adherent population. Cytokine induction require d the presence of interferon-gamma and either tumor necrosis factor-al pha or lipopolysaccharide. L-arginine dependence was demonstrated by i nhibition with an L-arginine analog and restoration with addition of e xcess L-arginine.