NOS2 and colitis: IM may contribute directly to the pathology of STm-induced colitis by producing proinflammatory cytokines (e. g., TNF-α) and indirectly by licensing other cells (e. g., NK cells, γ:δ T cells, intraepithelial lymphocytes, group 3 innate lymphocytes) to produce proinflammatory cytokines (e. g., TNF-α, IFN-γ, IL-22), some of which, as stated above, can potentiate epithelial Nos2 expression.