Nitric oxide production by macrophages stimulated by antigen-binding T-cell factors

Contact sensitivity to small molecular weight compounds is accompanied by the production of antigen-specific T-cell factors (TCF) shortly after skin application of the sensitizing agents. In this study, we show that macrophages can be activated by these TCF to generate large amounts of nitric oxide (NO). Incubation of the murine macrophage cell line J774 for 24 h with TCF raised against dinitrofluorobenzene (DNFB) or picryl chloride (PCL) resulted in a nitrite accumulation in the culture medium. Priming of J774 with rIFN-gamma synergistically enhanced stimulation of NO synthesis by DNFB-F and PCL-F. A possible contribution of lipopolysaccharide (LPS) as a contaminant of the TCF was excluded. The enhanced production of NO after stimulation with TCF was accompanied with an increased expression of inducible NO synthase. Inclusion of inhibitors of protein tyrosine kinase and protein kinase C inhibited the TCF-induced NO production by macrophages, indicating the involvement of both protein kinases in the signaling pathway activated by TCF. Since NO is an important biological mediator with many immunoregulatory properties, our results suggest a potential role for increased NO production by macrophages in the elicitation of contact sensitivity to small molecular weight compounds.