Table 1 |.

Role of IL-23 in mucosal homeostasis and disease

Cell type	Pathway and/ or signalling molecules	Effect
Innate immune system
Type 3 innate lymphoid cell	IL-23R/STAT5	Cell activation Cytokine production (IL-17A, IL-22) Antimicrobial effects
Granulocyte	IL-23R	Cell activation Pro-inflammatory cytokine production
Natural killer/intraepithelial lymphocytes	IL-23R	Cytotoxicity Cell activation Pro-inflammatory cytokine production
Adaptive immune system
Treg Cells, Teff cells, TH17 cells	IL-23R RORγt (Teff cells)	Suppression of Treg cells Proliferation and expansion of TH17 cells Production of IL-6 and TH17 cytokines
Intestinal epithelial cells	IL-22 Regenerating gene family proteins	Increased barrier function Antimicrobial effects

Interleukin-23 (IL-23) exerts effects on both innate and adaptive immune cells. In type 3 innate lymphoid cells, granulocytes, intraepithelial lymphocytes and natural killer cells, IL-23 induces cell activation and cytokine production. Additional effects of IL-23 are related to adaptive immune cells, such as regulatory T (T_reg) cells, and effector T (T_eff) cells, such as T helper 17 (T_H17) cells. In this context, IL-23 suppresses T_reg cells, whereas it activates T_H17 cells. Furthermore, this cytokine regulates barrier function and production of antimicrobial peptides in intestinal epithelial cells. IL-23R, IL-23 receptor; RORγt, retinoid-related orphan receptor-γt; STAT, signal transducer and activator of transcription.