The existence of a predictive serum biomarker of response or nonresponse to anti-TNFα therapy would improve the management of patients by avoiding delaying the use of potentially more effective treatment in patients Priori non-responders to an anti-TNF α biotherapy. If approximately 25% of the patients are not responding to a first biotherapy, it would be interesting to be able to identify them upstream, using a predictive marker, in order to orient them early to another therapy.