Clonal Distribution of B Cells Between Distant Foci of Gut-Associated Lymphoid Tissue in Humans.

Gut-associated lymphoid tissue (GALT) in humans is not easily visible to the naked eye, even from the luminal surface of the gut.  However, lymphoid follicles can be observed through the colonoscope and can be selectively biopsied.  So far, only B cells isolated from the relatively prominent follicles of the Peyer’s patches sampled at endoscopy have been studied in cell suspensions.  Here we compare B cells from three sites in the gut by flow cytometry and we compare the clonal distribution of B cells between these sites by next generation sequencing. The three sites compared were the Peyer’s patches of the terminal ileum, the prominent follicles located around the mouth of the appendix and the follicles in the rectum.

We have observed that the cellular composition of GALT in the three sites is similar.  All sites contain germinal centre, naïve and marginal zone B cells and the T2 but not T1 subsets of transitional B cells and the proportions of each are similar in each site. We observed IL-10 production by B cells at all sites that was higher than production by B cells in the blood and that was highest by the T2 subset of transitional B cells in GALT.

B cells clones identified by next generation sequencing were common to all three sites in the gut in 4 tissue donors studied in this way.  The features of these clones and their distribution across B cell subsets will be discussed.