Inflammatory bowel disease (IBD) is a chronic inflammatory disease associated with increased risk of gastrointestinal cancers. We whole-genome sequenced 446 colonic crypts from 46 IBD patients and ...compared these to 412 crypts from 41 non-IBD controls from our previous publication on the mutation landscape of the normal colon. The average mutation rate of affected colonic epithelial cells is 2.4-fold that of healthy colon, and this increase is mostly driven by acceleration of mutational processes ubiquitously observed in normal colon. In contrast to the normal colon, where clonal expansions outside the confines of the crypt are rare, we observed widespread millimeter-scale clonal expansions. We discovered non-synonymous mutations in ARID1A, FBXW7, PIGR, ZC3H12A, and genes in the interleukin 17 and Toll-like receptor pathways, under positive selection in IBD. These results suggest distinct selection mechanisms in the colitis-affected colon and that somatic mutations potentially play a causal role in IBD pathogenesis.
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•IBD-affected colons accrue substitutions and indels 2.4 and 7 times faster than normal•17 signatures of mutational processes, including treatment•Millimeter-scale clonal expansions late in molecular time•Distinct mechanisms of positive selection of mutations in immune-related genes
Whole-genome sequencing of inflammatory bowel disease patient samples allows insight into mutational burdens and processes associated with disease, including putative driver mutations positively selected in the diseased colon.
Inflammatory bowel disease is a chronic, relapsing condition with two subtypes, Crohn’s disease (CD) and ulcerative colitis (UC). Genome-wide association studies (GWASs) in UC implicate a FCGR2A ...variant that alters the binding affinity of the antibody receptor it encodes, FcγRIIA, for immunoglobulin G (IgG). Here, we aimed to understand the mechanisms whereby changes in FcγRIIA affinity would affect inflammation in an IgA-dominated organ. We found a profound induction of anti-commensal IgG and a concomitant increase in activating FcγR signaling in the colonic mucosa of UC patients. Commensal-IgG immune complexes engaged gut-resident FcγR-expressing macrophages, inducing NLRP3- and reactive-oxygen-species-dependent production of interleukin-1β (IL-1β) and neutrophil-recruiting chemokines. These responses were modulated by the FCGR2A genotype. In vivo manipulation of macrophage FcγR signal strength in a mouse model of UC determined the magnitude of intestinal inflammation and IL-1β-dependent type 17 immunity. The identification of an important contribution of IgG-FcγR-dependent inflammation to UC has therapeutic implications.
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•Intestinal inflammation in UC is associated with increased anti-commensal IgG•Commensal-IgG cross-link FcγR on colonic MNPs, inducing IL-1β production•MNP FcγR A:I ratio determines magnitude of type 17 immunity and local inflammation•Identifies cellular mechanisms by which FcγRIIA H/R131 confers UC susceptibility
Castro-Dopico et al. find a profound induction of anti-commensal IgG in the colonic mucosa of UC patients and outline a pathway whereby FcγR receptor activation by IgG leads to IL-1β production, type 17 immunity, and the exacerbation of inflammation. Their findings reveal an important contribution of IgG-mediated inflammation in an IgA-dominated organ.
Methotrexate (MTX) has been utilized for the treatment of Crohn's disease (CD) for decades. Nevertheless, current data provide equivocal evidence on the efficacy of MTX in CD.The aims of this study ...were to describe the efficacy of MTX for maintenance of remission in CD and to identify the factors associated with the probability of steroid-free clinical remission in a multicenter European referral center cohort.
This was a retrospective cohort analysis. Consecutive patients treated with MTX for CD were included from 11 referral centers. Patients receiving concomitant treatment with tumor necrosis factor inhibitors or thiopurines were excluded. The main outcome was steroid-free clinical remission; the secondary outcomes included the rate of complications leading to MTX discontinuation and duration of relapse-free survival in patients achieving the main outcome.
Between July 1992 and January 2012, 118 patients were identified for inclusion. MTX administration route was oral for induction in 31.4% and for maintenance in 49.1% of the patients. Steroid-free remission was achieved in 44/118 (37.2%) patients and was maintained relapse free by 28/44 (63.6%) for a median of 12 (3.5-18.5) months. At least one adverse effect was reported by 28.9% of the patients. No clinical or demographic factors were associated with either likelihood of achieving a clinical response or duration of relapse-free survival.
MTX treatment induced steroid-free clinical remission in over a third of CD patients and maintained it for a year in almost two-thirds of the responders. MTX should be considered a viable therapeutic option in CD patients refractory to other therapies.
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