IL-12 beta

Interleukin-12 subunit beta (IL-12B, commonly p40) is the 40 kDa shared subunit of two distinct heterodimeric cytokines: IL-12 (paired with p35/IL-12A) and IL-23 (paired with p19/IL-23A). Structurally it comprises two fibronectin type III domains, an Ig-like domain and a WSXWS motif, resembling a soluble cytokine receptor fused to a cytokine chain. p40 is produced by dendritic cells, macrophages, B cells and neutrophils after TLR or CD40 stimulation, and is additionally secreted as a monomer and disulfide-linked homodimer (p80) with distinct functions: p40 monomer antagonizes IL-12 signaling, p80 signals through IL-12Rβ1 to drive TNF and nitric oxide production in macrophages and neuropathic pain. Polymorphisms in IL12B influence susceptibility to tuberculosis, type 1 diabetes and psoriasis; the anti-p40 antibody ustekinumab blocks both IL-12 and IL-23 and is highly effective in psoriasis and Crohn's disease.