FIG. 1.

Triggering NO production by treatment of TNFR^−/− PECs with anti-CD3. Resident PECs pooled from three to five wild-type, TNFRp55^−/−, or TNFRp55p75^−/− mice were cultured with medium, IFN-γ (100 U/ml), IFN-γ plus LPS (100 ng/ml), or soluble anti-CD3 MAb 145-2C11 (5 μg/ml) for 72 h, at which time NO₂ was measured in supernatants by using the Greiss reagent. Cultures were normalized to contain 10⁶ macrophages/ml. Left, PECs (10 to 20% CD4⁺ T cells; 50 to 60% Mac-1⁺ F4/80⁺ B220⁻ CD19⁻ T cells). Right, PECs plus nylon wool-enriched splenic T cells from naive mice (ratio, 1 T cell/1 macrophage). T cells incubated without macrophages in the presence of anti-CD3 or IFN-γ and LPS produced less than 10 μM NO₂ (data not shown). Limit of detection for all Greiss reactions was 4 μM. The data represent one experiment showing the mean NO₂ production of duplicate cultures (±SE). Similar results were obtained from four additional experiments.