In order to understand why some patients suffering from UC do not benefit from anti-TNFa treatments like infliximab, an international study was launched under the impetus of the University Hospital of Louvain in Belgium. The team of Paul Rutgeerts carried out a wide-scale study of gene expression in the intestinal mucosa of patients treated with infliximab. Expression profiles were compared between responders and non-responders so as to reveal a “signature” enabling prediction of response to treatment. This study led to defning of 5 overexpressed genes in patients with UC who were non-responders to infliximab. These markers were able to differentiate responders from non-responders with a sensitivity of 95% and a specificity of 85%. This represents a highly interesting tool for clinical practitioners in management of patients with UC.