Unlike ordinary inflammation, fibrosis involves the excessive production and accumulation of connective tissue proteins, including collagen. By comparing gene-expression patterns across disease states, researchers can identify biological pathways that become more active or less active as disease progresses. Genes associated with digestion, nutrient absorption and maintenance of the intestinal lining were less active in fibrotic tissue. Patients with fibrotic disease showed reductions in several bacteria commonly associated with the production of short-chain fatty acids, including Faecalibacterium, Anaerostipes, Coprococcus and Ruminococcus. Interleukin-23 receptor, or IL-23R, participates in immune pathways involved in chronic intestinal inflammation.