Influence of the gut and cytokine patterns in spondyloarthropathy

Clinical and histological studies have previously shown that spondyloarthropathy (SpA) patients can have subclinical gut inflammation. This gut inflammation is related to enterocolitis in Crohn's disease (CD) and may evolve to overt inflammatory bowel disease in a subset of these patients. Moreover, there is an intriguing clinical link between gut inflammation and peripheral joint inflammation. In order to explore immunologically these concepts, recent studies have characterized phenotypically and functionally the inflammatory cells in both the gut and the synovium of SpA patients and have provided a number of new insights. Firstly, they confirm histological and pre-histological alterations of the gut immune system in SpA, which are redundant of CD and which are linked to alterations of the peripheral joints. Secondly, both the acquired and the innate immune system contribute to these alterations, with an important role for both T cells and macrophages and their cytokines. Thirdly, interpretation of these data support the hypothesis that gut and joint inflammation in SpA are induced by the combination of an impaired anti-bacterial host defence and an uncontrolled pro-inflammatory response of the innate immune system. The insights provided by the study of the gut immunology in SpA have contributed to develop new therapeutic strategies, with TNFalpha blockade as prototype.