TNF and inflammatory bowel disease: Also, administration of an IL-23 plasmid to IL-12p40−/− mice up-regulates production of IFN-γ in response to Mycobacterium tuberculosis [26] and IL-23 promotes IFN-γ production, rather than IL-17 production, via an IL-23– and TNF-α–dependent pathway in human inflammatory bowel disease [27].