The Influence of Infliximab and Adalimumab on the Expression of Apoptosis-related Proteins in Lamina Propria Mononuclear Cells and Enterocytes in Crohn's Disease - an Immunohistochemical Study

Background And Aims: The aim of this study was to assess the influence of anti-TNF agents on the expression of apoptosis-related proteins in Crohn's disease (CD) patients.

Methods: The clinical, biochemical and endoscopic activity of CD was assessed with the use of tissue sampling before the initiation of therapy and after induction doses of infliximab and adalimumab. Additionally, the immunohistochemical expression of active caspase 3, TNFR1, Fas, Bcl-2, Bax, CD4 and CD8 proteins was estimated. Patients achieving deep remission were considered as responders.

Results: Of the 35 patients qualified for the study, 60% achieved deep remission. In those patients, a significant decrease in the number of CD4 and CD8 positive cells was noted. Also observed was a significant increase in the expression of active caspase 3 in lamina propria mononuclear cells, which correlated with an increase of the pro-apoptotic Bax/Bcl-2 ratio. No change in Fas and TNFR1 expression was observed in those cells. Moreover, there was a significant decrease in active caspase 3 expression in enterocytes, observed independently of the Bax/Bcl-2 ratio. This correlated with a change in TNFR1 expression. No significant changes in the expression of the investigated proteins were noted in non-responders group.

Conclusions: The efficacy of anti-TNF antibodies is, at least partly, dependent on apoptosis modulation. In lamina propria mononuclear cells, the increase of apoptosis is probably the result of the induction of the intrinsic pathway mediated by Bcl-2 family proteins. In enterocytes - the decrease of apoptosis is mediated by the extrinsic pathway, probably via TNFR1.