Tumour necrosis factor alpha down-regulation parallels inflammatory regression in ulcerative colitis patients treated with infliximab

BACKGROUND: Treatment with the anti-tumour necrosis factor alpha monoclonal antibody infliximab has been shown to be effective in moderate-to-severe ulcerative colitis. However, its effect on the mucosal histopathological abnormalities of this disease is largely unknown. This study aimed to assess the immunohistological effect of infliximab in ulcerative colitis. METHODS: Nine patients with moderate-to-severe ulcerative colitis received infliximab (5mg/kg) at weeks 0, 2 and 6, respectively. Colonic biopsies were collected before therapy and at week 10, when the Mayo score (including the endoscopic subscore) was also assessed. Severity of inflammation was evaluated by histologic score and histomorphometry. Immunohistochemical staining with antibody against tumour necrosis factor alpha was performed on all biopsies and expressed as percentage of positive stromal cells/1000 counted (tumour necrosis factor alpha score). RESULTS: A profound down-regulation of mucosal tumour necrosis factor alpha occurred in all the six patients who achieved a clinical response, but not in the three who did not respond. Median tumour necrosis factor alpha score dropped from 44.8 (range 35-58.3) to 12.8 (range 5.3-15.3) in the responders (p=0.03), whilst it remained unchanged in the non-responders. Such effect was related with a dramatic regression of the median histologic score, which dropped from 2.7 (range 2-3) to 0.5 (range 0.0-1.5) in responder patients (p=0.002). This was related to a virtual disappearance of neutrophils in responders (r=0.72; p=0.002; Spearman's test), but not in those who did not improve. Tumour necrosis factor alpha score appeared to be correlated with the histologic, endoscopic and clinical activity. CONCLUSIONS: A profound tumour necrosis factor alpha down-regulation appears to be strictly associated with a dramatic regression of the inflammation in patients with moderate-to-severe ulcerative colitis treated with infliximab. Such immunohistochemical effect seems to be critical for a clinical and endoscopic response to therapy.