Interleukin 12 (IL-12) family

The interleukin 12 (IL-12) family is unique in having the only heterodimeric cytokines, including IL-12, IL-23, IL-27 and IL-35. This family also has many molecular and functional characteristics that provide unique opportunities for positive and negative feedback control, and some additional features may still be identified. IL-12 is composed of p35 and p40 subunits. IL-23 is composed of the IL-12p40 subunit and the IL-23p19 subunit, which shares homology with IL-12p35. IL-27 is composed of EBI3/IL-27B and p28. IL-35, a novel member of IL-12 family, is composed of the IL-12p35 and EBI3 subunits. IL-35 is secreted by regulatory T cells, and suppresses inflammatory responses of immune cells.