IL33 and rheumatoid arthritis: In particular, IL-1 has been identified as a critical factor in the differentiation and activation of Th17 cells, which mediate the development of autoimmune and inflammatory diseases, such as rheumatoid arthritis (RA), systemic lupus erythematosus, multiple sclerosis, psoriasis, and inflammatory bowel disease (IBD; Mills, 2011); whereas, IL-33 has been implicated in the initiation and propagation of Th2 immune responses, involved in allergy and asthma (Lloyd, 2010).