A broad term used to described natural chemicals (cytokines) produced by white blood cells for cell-to-cell communication.
Interleukins, like other cytokines, are often involved in stimulating or suppressing the immune system and inflammation (as is the case with their role in psoriasis). Another example of a cytokine important in psoriasis is TNF-alpha.
Interleukins are typically referred to by number, for example: IL-1, IL-2, etc. Recent studies have shown that IL-12 and IL-23 are very important in the development of psoriasis. The two are closely related and share a significant portion of their design; in fact, recent biologic drugs for psoriasis treatment have been developed to block IL-12/IL-23 simultaneously.