Crohn's Patients and Healthy Infants Share Immunodominant B Cell Response to Commensal Flagellin Peptide Epitopes.

Background & Aims: Inflammatory bowel disease (IBD) is a chronic manifestation of dysregulated immune response to the gut microbiota in genetically predisposed hosts. Nearly half of patients with Crohn's disease (CD) develop selective serum immunoglobulin (Ig)G response to flagellin proteins expressed by bacteria in the Lachnospiraceae family. This study aimed to identify the binding epitopes of these IgG antibodies and assess their relevance in CD and in homeostasis.

Human intestinal stromal cells promote homeostasis in normal mucosa but inflammation in Crohn's disease in a retinoic acid-deficient manner.

Intestinal stromal cells (SCs), which synthesize the extracellular matrix that gives the mucosa its structure, are newly appreciated to play a role in mucosal inflammation. Here, we show that human intestinal vimentinCD90smooth muscle actin SCs synthesize retinoic acid (RA) at levels equivalent to intestinal epithelial cells, a function in the human intestine previously attributed exclusively to epithelial cells. Crohn's disease SCs (Crohn's SCs), however, synthesized markedly less RA than SCs from healthy intestine (normal SCs).

Microbiota dictate T cell clonal selection to augment graft-versus-host disease after stem cell transplantation.

Allogeneic T cell expansion is the primary determinant of graft-versus-host disease (GVHD), and current dogma dictates that this is driven by histocompatibility antigen disparities between donor and recipient. This paradigm represents a closed genetic system within which donor T cells interact with peptide-major histocompatibility complexes (MHCs), though clonal interrogation remains challenging due to the sparseness of the T cell repertoire. We developed a Bayesian model using donor and recipient T cell receptor (TCR) frequencies in murine stem cell transplant systems to define limited common expansion of T cell clones across genetically identical donor-recipient pairs.

Crohn's patients and healthy infants share immunodominant B cell response to commensal flagellin peptide epitopes.

About half of patients with Crohn's disease (CD) develop selective serum IgG response to flagellin proteins of the family. Here, we identified a dominant B cell peptide epitope in CD, locating in the highly conserved "hinge region" between the D0 and D1 domains at the amino-terminus of flagellins. Serum IgG reactive to this epitope is present at an elevated level in adult CD patients and in pediatric CD patients at diagnosis.

Remodeling of colon plasma cell repertoire within ulcerative colitis patients.

Plasma cells (PCs) constitute a significant fraction of colonic mucosal cells and contribute to inflammatory infiltrates in ulcerative colitis (UC). While gut PCs secrete bacteria-targeting IgA antibodies, their role in UC pathogenesis is unknown. We performed single-cell V(D)J- and RNA-seq on sorted B cells from the colon of healthy individuals and patients with UC.