Wnt signalling influences T cell phenotype in a novel intestinal immune system model

Inflammatory bowel disease (IBD) is a collective term for inflammatory conditions that affect the gastro-intestinal tract. These conditions feature a multifactorial etiology: an interplay of genetics, environmental exposures, the immune system and commensal microbiota, all of which converge at the intestinal epithelia. The ability to understand IBD is dependent on and limited by the model systems used to study it. We have developed an ex vivo model of the human intestine by co-culturing intestinal organoids and PBMCs from the same patient. As intestinal organoids accurately mimic the intestinal epithelia, this allows us to study the interaction of the epithelium and immune system on a controlled genetic background in both IBD patients and healthy individuals. I hypothesise that intestinal organoids cultured with immune cells will create an environment similar to the human intestinal immune environment. The aim of my research was to develop a platform to study the role of immune cells in this organoid culture. I analysed the effect of organoid culture conditions on the survival and phenotype of immune cells, measured by cytokine and cell surface receptor expression. PBMCs remained viable for four days when grown in DMEM, and this viability was not affected by suspending the cells in the Matrigel used for organoid culture. Freezing and thawing PBMCs, which is required to allow establishment of the organoids, only caused a slight reduction in viability, and did not affect the frequency of Th1, Th17 and regulatory T cells. Introduction of growth factors required for organoid culture did not affect viability of the PBMCs, however the frequencies of Th1 and Th17 but not regulatory T cells were reduced. Recombinant Wnt, a key component used to culture organoids, affected the ability of regulatory T cells to maintain but not differentiate their phenotype. Finally, viable T cells could be removed from a complete PBMC-organoid co-culture. These data indicate that PBMCs can be successfully cultured in conditions used to generate intestinal organoids without loss of viability or major changes in phenotype. Furthermore, this co-culture model will likely serve as an accurate model of the intestinal immune system and may aid in the search of an effective treatment for IBD