To Örebro University

Background: Soluble factors released by intestinal mucosal cells contribute to immune homeostasis in the gut. This is the first study to investigate the role of soluble factors from the intestinal mucosa of collagenous colitis (CC) patients in the regulation of effector T cells using a novel system that mimics the in vivo exposure of newly recruited peripheral blood T cells to soluble factors derived from the colonic milieu of normal individuals and inflamed CC patient mucosa.

Methods: Denuded biopsies (DNB) and isolated lamina propria mononuclear cells (LPMCs) from mucosal biopsies from CC patients and non-inflamed controls were cultured to collect conditioned medium (CM). Enriched peripheral blood CD4⁺ T cells from healthy donors were polyclonally activated in the absence or presence of CM from CC patients and controls. Proliferation, as well as secretion of IL-1β IL-4, IL-6, IL-10, IL-17A, IFN-γ and TNF-α was analysed the latter with Luminex® analysis.

Results: Peripheral CD4⁺ T cells exposed to CM from the colonic mucosa demonstrated reduced proliferation. This inhibition was less pronounced with DNB-CM derived from CC patients compared to non-inflamed control mucosa. In contrast, LPMC-CM from non-inflamed controls inhibited T-cell proliferation less than LPMC-CM from CC patients. Both DNB-CM and LPMC-CM from CC patients induced more or less increased production of the proinflammatory cytokines IFN-γ, IL-17A, IL-6 and TNF-α as well as the anti-inflammatory cytokines IL-4 and IL-10 from peripheral CD4⁺ T cells compared to non-inflamed controls. In contrast, IL-1β production by peripheral T cells showed mixed results – it was either increased or reduced in the presence of both DNB and LPMC-CM from CC patients compared to noninflamed controls with different blood donors and different concentrations.

Conclusion: Our preliminary data indicates reduced inhibition of proliferation of peripheral CD4⁺ T cells in the presence of mucosa-derived soluble factors from CC patients compared to controls. In addition, increased production of both inflammatory and anti-inflammatory cytokines by peripheral CD4⁺ T cells was recorded in the presence of soluble factors from the colonic mucosa of CC patients compared to controls. This model can be valuable in evaluating the effect(s) of existing and new drugs on T cell differentiation in the intestinal mucosa.