Interleukin-23 (IL-23) was first reported in 2000, when a new sequence (p19) was discovered, which binds to the p40 subunit of IL-12, resulting in a new biologically active cytokine complex. It is secreted by activated dendritic cells, showing both similarities and differences in biological characteristics compared to IL-12.
IL-23 belongs to the IL-12 cytokine family, which also includes members like IL-12, IL-27, IL-35, and IL-39. These are unique heterodimeric cytokines, typically composed of an α-chain subunit (p19, p28, or p35) and a β-chain subunit (p40 or Epstein-Barr virus-induced gene 3), signaling through the JAK/STAT pathway. IL-23 binds to its receptor complex consisting of IL-23R and p40 subunit to transmit signals, similar to how IL-12 signals through its p35 and p40 subunits binding to IL-12Rβ2 and IL-12β1 subunits of the IL-12 receptor.
IL-23 receptor is predominantly expressed on natural killer cells, macrophages, memory T cells (Th17), and keratinocytes. In response to microbial pathogens or wound healing signals, IL-23 is produced by activated dendritic cells and macrophages, accompanied by recruitment of neutrophils.
