Phenotypic analysis of intestinal non-inflamed mucosa in Crohn's disease: evidence of mononuclear cell depletion in lamina propria.

Objective: The objective of this study was to examine mononuclear cell subpopulations and evidence of cellular activation in unaffected jejunal mucosa in Crohn's disease.
Design: A cross-sectional study was performed in patients with Crohn's disease from the ambulatory unity of the University Hospital, UFRJ.
Methods: Mucosal samples from 20 patients with Crohn's colitis or ileitis were obtained by peroral jejunal biopsy. Patients with jejunal involvement or pregnant women were excluded from the study. Specimens were analysed histologically and by indirect immunoperoxidase method using anti-monoclonal antibodies to CD2, CD4, CD8, CD25, CD45RO, RFDR1, RFD1 and RFD7 by two 'blind' observers. Seven patients with non-inflammatory bowel disorders and two healthy volunteers were studied as controls.
Results: Lamina propria CD2-positive (CD2+) cells were reduced in Crohn's disease (P < 0.004) whether clinically active (P < 0.02) or clinically inactive (P < 0.008). CD4+ and CD8+ cells were also reduced in Crohn's disease (P < 0.003), whereas the CD4:CD8 ratio did not differ from that in controls. CD25+, CD45RO+ and HLA-DR+ cells were not significantly increased in patients with Crohn's disease. RFD7+ cells were decreased in Crohn's disease (P < 0.02), whereas RFD1+ cells were not significantly different from the control group.
Conclusion: No evidence of cellular activation was found in the unaffected mucosa of Crohn's disease. The reduction in T-cell and macrophage-like cell numbers may result from cell migration to inflamed areas. It is also possible that this finding represents a primary defect which may have a role in the pathogenesis of Crohn's disease.