The results of the SONIC trial represented a significant advance in the management of patients with chronic inflammatory bowel disease by demonstrating the superiority of the combination of an alpha TNF anti-TNF with immunosuppressive therapy in naive patients (infliximab and azathioprine) compared to monotherapy in terms of clinical and endoscopic remission (40% versus 22%, p = 0.017). The benefit of this combination therapy is both pharmacological (addition, or even synergy of the two treatments) and immunological (reduction of the risk of immunization to biotherapy).||Data on the use of immunosuppressive methotrexate treatment are divergent. Indeed, a previous randomized trial suggested that the combination of anti-TNF alpha including infliximab and methotrexate was no more effective than anti-TNF alpha monotherapy in patients with Crohn's disease. However, the superiority of this combination has been clearly demonstrated over monotherapy in rheumatology for a long time.||In practice, more and more practitioners are prescribing this combination (antiTNF and MTX) in IBD patients because of tolerance problems, particularly to azathioprine or in patients with a dual expression of their disease, both digestive and joint.||The interest of my thesis work is therefore to be able to clarify these grey areas and to be able to modify or comfort therapeutic choices in practice.