Monocytes, macrophages, fibroblasts, endothelial cells, keratinocytes, mast cells, T cells, and some tumor cells have the capacity to produce IL-6.19 Serum IL-6 levels increase in a wide variety of inflammatory processes, such as sepsis, autoimmune diseases, lymphoma, AIDS, alcoholic liver disease, infections, and acute graft-versus-host disease. Here, IL6 is linked to acute graft versus host disease.