Interleukin 32 (IL-32), previously known as a transcript (NK4), is produced by mitogen-activated lymphocytes, by IFNγ-activated epithelial cells or by IL-12 and IL-18-activated NK cells. Its expression is increased following activation of T-cells by mitogens or the activation of NK cells by IL-2. IL-32 activates NF-κB and p38 MAPK cytokine signal pathways. It has been suggested that IL-32 may play a role in autoimmune and inflammatory diseases such as rheumatoid arthritis. IL-32 is unusual in that it does not share sequence homology with known cytokine families and is highly expressed in immune tissues. IL-32 exists in at least four differentially spliced isoforms (α, β, γ and δ)with predicted molecular weight: ~26 kD. IL-32α is the shortest and most abundant of four potential splice variants of the pro-inflammatory cytokine IL-32. Potential modifications include myristoylation and N-glycosylation. Transfected IL-32α was more likely to be cell-associated as compared to IL-32β, suggesting an intracellular function.