Infliximab reduces the number of activated mucosal lymphocytes in patients with Crohn's disease.

Background: Infliximab is an effective treatment for Crohn's disease in patients with poor prior response to conventional therapy. The mechanism by which infliximab induces clinical improvement is not completely known.

Aim: The aim of the study was to investigate the influence of infliximab on immunological parameters in peripheral blood and inflamed intestinal mucosa.

Methods: Twenty-five patients with Crohn's disease (11 with luminal and 14 with fistular form) underwent treatment with infliximab. The lymphocyte populations from the peripheral blood and the inflamed intestinal mucosa were analysed by flow cytometry before treatment and 14 days later.

Results: After treatment, the peripheral blood analysis showed a significant increase in the percentage of CD19 cells and the concentrations of CD3, CD4, CD8 and activated (HLA DR positive) T cells, while the percentage of NK cells was reduced. In the inflamed mucosa, a significant decrease in the percentage of activated T cells and expression of HLA I molecules by epithelial cells was noted.

Conclusions: Infliximab profoundly downregulates inflammation in the intestinal mucosa of patients with Crohn's disease. This effect is manifested by a reduction of activated T cells, main producers of proinflammatory cytokines, in the inflamed mucosa.