text: Monocytes, activated dendritic cells (DC) and macrophages stimulate the accumulation of IL-23 after exposure to molecules of Gram-positive/negative bacteria or viruses. Receptor for IL-23 contains IL12β and IL23R subunits, which upon binding of IL-23 promotes the phosphorylation STAT4. The presence of IL12β enables similar, although weaker downstream activity as compared to IL-12. During chronic inflammation, IL-23/STAT4 signalling pathway is involved in the induction of differentiation and expansion of Th17 pro-inflammatory T helper cells.
  Additionally, other cytokines like IL2, IL 27, IL35, IL18 and IL21 are known to activate STAT4.