T Cell Repertoire Homogeneity and Blood-Gut Overlap in Patients With Inflammatory Bowel Disease.

BACKGROUND & AIMS: Inflammatory bowel disease (IBD) causes a marked increase in the number of T cells in the intestinal mucosa. Debate exists about whether these excess cells arise from local clonal proliferation or recruitment from the periphery. METHODS: CD8+ T cells were sorted from colon biopsy specimens and blood for T-cell receptor (TCR) ß-chain sequencing. Biopsy specimens from inflamed or uninflamed colon from ulcerative colitis or Crohn's disease cohorts were compared with colon biopsy specimens from people without IBD, as well as with autologous blood α4ß7+, α4ß7- effector/memory, terminal effector/memory CD45RA+ T cell, and mucosal-associated invariant T-cell CD8 subpopulations. RESULTS: CD8 TCR diversity in mucosa and blood did not correlate with inflammation. Repertoire overlap between any 2 distinct locations of a given person's colon was consistently high, although often lower between inflamed and uninflamed sites. CD8 TCR repertoires overlapped between the colon and each peripheral blood subpopulation studied, with the highest overlap seen for integrin α4ß7+ T cells. Inflamed tissue consistently overlapped more than uninflamed tissue with each blood subpopulation. CONCLUSIONS: CD8 T-cell clones are spread homogenously throughout the length of the colon. Although TCR repertoire overlap is greater within than between inflamed and uninflamed colon segments, a similar TCR diversity in both argues against local clonal expansion being the main source of excess cytotoxic T cells in inflamed mucosa. Rather, the increased TCR overlap observed between blood and inflamed mucosa supports the significance of T-cell trafficking in IBD pathogenesis, particularly concerning α4ß7+ T-cell populations.

Proteomic Differences in Colonic Epithelial Cells in Ulcerative Colitis Have an Epigenetic Basis.

Background and Aims: The colonic epithelium serves as both a barrier to lumenal contents and a gatekeeper of inflammatory responses. In ulcerative colitis (UC), epithelial dysfunction is a core feature, but little is known about the cellular changes that may underlie disease pathology. We therefore evaluated how the chromatin epigenetics and proteome of epithelial cells differs between health and UC. Methods: We sorted live CD326+ epithelial cells from colon biopsies of healthy control (HC) screening colonoscopy recipients and from inflamed or uninflamed colon segments of UC patients on no biologic nor immunomodulator therapy (n = 5-7 subjects per group). Cell lysates were analyzed by proteomic evaluation and nuclei were analyzed for open chromatin with assay for transposase-accessible chromatin using sequencing. Results: Proteins most highly elevated in inflamed UC biopsies relative to HC were those encoded by the HLA-DRA (P = 3.1 × 10-33) and CD74 (P = 1.6 × 10-27), genes associated with antigen presentation, and the antimicrobial dual oxidase 2 (DUOX2) (P = 3.2 × 10-28) and lipocalin-2 (P = 2.2 × 10-26) genes. Conversely, the water channel aquaporin 8 was strikingly less common with inflammation (P = 1.9 × 10-18). Assay for transposase-accessible chromatin using sequencing revealed more open chromatin around the aquaporin 8 gene in HCs (P = 2.0 × 10-2) and more around the DUOX2/DUOXA2 locus in inflamed UC colon (P = 5.7 × 10-4), suggesting an epigenetic basis for differential protein expression by epithelial cells in health and disease. Conclusion: Numerous differences exist between the proteome and chromatin of colonic epithelial cells in UC patients and HCs, some of which correlate to suggest specific epigenetic mechanisms regulating the epithelial proteome.

Vedolizumab Efficacy Is Associated With Decreased Intracolonic Dendritic Cells, Not Memory T Cells.

BACKGROUND: Vedolizumab, an antibody blocking integrin α4ß7, is a safe and effective therapy for Crohn's disease and ulcerative colitis. Blocking α4ß7 from binding its cognate addressin MAdCAM-1 on intestinal blood vessel endothelial cells prevents T cells from migrating to the gut mucosa in animal models. However, data supporting this mechanism of action in humans is limited. METHODS: We conducted a cross-sectional case-control study to evaluate the effect of vedolizumab on intestinal immune cell populations while avoiding the confounding effect of resolving inflammation on the cellularity of the colonic mucosa in treatment-responsive patients. Colon biopsies from 65 case subjects receiving vedolizumab were matched with biopsies from 65 control individuals, similar in disease type, medications, anatomic location, and inflammation. Biopsies were analyzed by flow cytometry and full messenger RNA transcriptome sequencing of sorted T cells. RESULTS: No difference was seen between vedolizumab recipients and control individuals in the quantity of any antigen-experienced T lymphocyte subset or in the quality of the transcriptome in any experienced T cell subset. Fewer naïve colonic B and T cells were seen in vedolizumab recipients than control individuals, regardless of response. However, the most striking finding was a marked reduction in CD1c+ (BDCA1+) dendritic cells exclusively in vedolizumab-responsive patients. In blood, these dendritic cells ubiquitously express high levels of α4ß7, which is rapidly downregulated upon vedolizumab exposure. CONCLUSIONS: The clinical effects of vedolizumab reveal integrin α4ß7-dependent dendritic cell migration to the intestinal mucosa to be central to inflammatory bowel disease pathogenesis.

Vedolizumab had no effect on the number or gene expression of memory T lymphocytes in the colons of recipients relative to control individuals. However, the colons of vedolizumab-responsive patients had distinctly fewer dendritic cells, which in blood express the most integrin α4ß7.