Interleukin-32: a predominantly intracellular proinflammatory mediator that controls cell activation and cell death.

In this review, we will discuss the current knowledge on IL-32 and provide new insights regarding the biological function of IL-32. IL-32 is seen as a cytokine that can induce a range of proinflammatory mediators and contribute to autoimmune diseases, such as rheumatoid arthritis, however present knowledge demonstrates that IL-32 is not a classical cytokine. We present the history of this cytokine, the role of IL-32 in several diseases and discuss a possible novel role of intracellular IL-32 in cell homeostasis. Taken into account the observed biological functions of IL-32, it may belong to a class of cytokines, like IL-1α, IL-33, and IL-37, with both intracellular and extracellular functions.