Cytokines in disease

Cytokines are key mediators of inflammation prominently involved in autoimmune and inflammatory diseases. The cytokines of most relevance to rheumatic diseases also have important functions in many non-immune cell types, including fibroblasts, osteoblasts, osteoclasts and endothelial cells, beyond their well-described roles in the immune system. Advances in our understanding of cytokine biology are not only improving our knowledge of the pathogenetic mechanisms of diseases such as rheumatoid arthritis, osteoarthritis and systemic lupus erythematosus—disorders in which cytokines play a key part—but also driving the development of new therapeutic strategies. This fast-developing area of research is achieving notable success with approaches targeting cytokine-mediated mechanisms, and multiple studies are now underway to test the efficacy of cytokine signalling modulation in disease. In this Focus issue, the cytokine pathways at work in rheumatic diseases are explored, with an emphasis on the role of TNF, IL-1, GM-CSF, chemokines and type I and II cytokines in supporting inflammation and tissue destruction.