Autoimmunity in ulcerative colitis (UC): a predominant colonic mucosal B cell response against human tropomyosin isoform 5
In UC but not in CC and non‐IBD controls, the increased number of IgG‐producing cells are largely committed to produce IgG against hTM5‐related epitope(s), a putative autoantigen in UC.
Abstract
We set out to examine if the IgG‐producing cells in the colonic mucosa in UC are committed to tropomyosin isoform 5 (hTM5), a putative autoantigen in UC. Lamina propria mononuclear cells (LPMC) were isolated from colonoscopic biopsy specimens from recto‐sigmoid and proximal colon. Twenty‐three patients with UC, eight with Crohn's colitis (CC), and 10 non‐inflammatory bowel disease (non‐IBD) controls were included. The ELISPOT assays were used to quantify lamina propria B cells producing total immunoglobulin (IgA, IgG, IgM), IgG, IgA, as well as IgG against hTM5 isoform. The median value of percentage of total IgG‐producing lymphocytes was similar in UC (12%) and CC (11%), but was significantly (P < 0·0002) higher than non‐IBD controls (6%). However, in UC, but not in CC and non‐IBD, a large number of lamina propria B cells produced IgG against hTM5 (median values: UC 42%, CC 2·5%, non‐IBD 0%). This difference in UC when compared with CC and non‐IBD was highly significant (P < 0·00001). Twenty‐one of 23 (91%) patients with UC had percentage of anti‐hTM5 IgG‐producing immunocytes more than 2 s.d. above the mean for non‐UC patients. In UC but not in CC and non‐IBD controls, the increased number of IgG‐producing cells are largely committed to produce IgG against hTM5‐related epitope(s).