Nitric oxide production of macrophages stimulated by antigen-specific t cell factors

Contact sensitization of mice with small molecular weight compounds like picryl chloride (PCL) or dinitrofluorobenzene (DNFB) results in the production of an antigen-specific T cell factor (TCP), which is known to be involved mast cells (MC) activation. Activation of MC may play an important role in the contact hypersensitivity (CS) reactions elicited by PCL and DNFB. The role of macrophages (MØ) in these CS reactions is less well understood. TCP have been shown to activate MØ to produce e.g. IL-1, TNF-α, and PGE₂- Since MØ can also produce large amounts of nitric oxide (NO), a compound with important vasodilating and immune modulatory properties, we investigated the effects of TCP on the induction of NO synthesis by MØ. Murine MØ (J774) and freshly isolated rat peritoneal MØ were incubated with TCP and 24 h later supernatant was collected for nitrite analysis. TCP stimulated cells produced 1.5-3 nmol/10⁶ cells of nitrite. Increased NO production was accompanied with an upregulation of iNOS. Stimulation of the MØ was not due to LPS contamination of the TCF. Morphologically, activated MØ had a more elongated and flattened appearance. In TCP -induced activation of MØ both PKC and tyrosine kinases may be involved, since bisindolylmaleimide and genistein, respectively, inhibited nitrite production. In conclusion, this study provides evidence that MØ are activated by TCP to produce NO, which may play a role in the elicitation of CS to small molecular weight compounds. Sponsored by Glaxo and the Royal Dutch Academy of Arts and Sciences.