STAT1 and enthesitis: In addition, the proinflammatory cytokine burst, evidenced in myeloid cells during enthesitis, seems to be related to hyperreactive signaling via Signal Transducer and Activator of Transcription 1 (STAT1), and in the absence of the STAT1 counterregulatory protein A20, entheseal inflammation occurs spontaneously [29], strengthening the relevance of myeloid compartment in enthesitis pathophysiology.