Figure 5.

Suppression of T cell proliferation by M regs is mediated by inducible nitric oxide synthase. (a) Heatmap depicting relative expression of genes (median-centered log₂ signal intensities, n = 3) with known T cell-inhibitory functions in macrophages. (b) Screening of inhibitors of known T cell-suppressive mediators to identify the mechanism by which M regs prevent T cell proliferation in vitro. Only L-NMMA, an inhibitor of nitric oxide synthase, was found to inhibit M reg-mediated suppression of T cell division. (c) Using M regs generated from Nos2-deficient mice, inducible nitric oxide synthase (iNOS) was confirmed as the key mediator of T cell suppression by M regs. (d) Constitutive expression of iNOS expression in M regs was low, but was upregulated by coculture with ConA- and T-Stim-activated T cells and to a greater extent by treatment with a cocktail of lipopolysaccharides (LPS), interferon-γ (IFN-γ), interleukin (IL)-1β and TNF-α.