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P046. Lymphocytic and collagenous colitis: two clinically similar entities but with a distinct immunological pattern

A. Carrasco1, M. Esteve1, E. Pedrosa1, M. Rosinach1, M. Aceituno1, X. Andújar1, C. Loras1, Y. Zabana1, M. Forné1, A. Salas2, F. Fernández-Bañares1, 1Hospital Universitari Mútua Terrassa. UB, Gastroenterology, Terrassa, Spain, 2Hospital Universitari Mútua Terrassa, UB, Pathology, Terrassa, Spain

Background

The immunology of microscopic colitis (MC) is poorly understood and it is unknown whether the two forms of presentation, collagenous colitis (CC) and lymphocytic colitis (LC) share common mechanisms.

Methods

15 patients with CC and 7 with LC with untreated active disease were included. As a control group 10 patients with normal colonoscopy and colonic histology were also included. Left colon biopsies were taken for analysis of lymphocyte subpopulations by flow cytometry and cytokine production by qPCR.

Results

The absolute number of cells was significantly higher and the number of apoptotic cells (Caspase3+) lower in both CC and LC compared to controls. There were significant differences in lymphocyte subpopulations between CC and LC: the percentage of CD3+, CD3+CD8+, CD3+CD4+TCRγδ+, CD3+CD4−CD8− was increased in LC as compared to CC and controls, whereas the percentage of CD3+CD4+ and CD3+CD4+CD8+ was decreased in LC compared to CC and controls. In CC the percentages of these cell types did not differ from the control group. Moreover, Treg cells (CD4+CD25+FoxP3+) were significantly increased in both the CC and LC. In addition, an increase in CD4+CD25−FoxP3+ was observed in CL. Gene expression (measured as ‘fold Increase’ compared to controls) of IFNγ and IL-17A was increased in both types of MC, being higher in LC. In addition, IL15 mRNA was lower in both CC and LC, whereas IL10 was found increased in CL but not in CC.

Conclusion

We have detected remarkable differences in cellular immune response between CC and LC, suggesting that they do not share the same pathophysiological mechanisms. The decrease of apoptosis may play a role in the increased cellularity observed in both CC and LC.

Sponsored by a Basic Research Grant from Acadèmia de Ciències Mèdiques, Barcelona.