MoAb H81.9-induced nitric oxide (nitrite) generation in murine J774 cells is prevented by the NOS inhibitor NMMA. The vertical axis shows nmol of nitrite, the horizontal axis time after initiation of cultures. Results are expressed as the mean ± SEM of triplicate cultures of three to four experiments. Where indicated the NOS inhibitor NMMA at a concentration of 0.5 mmol/L was added concurrently with MoAb H81.9. (P < .05 at 48 and 72 hours for cells treated with H81.9 v untreated controls or cells treated with H81.9 + NMMA.)