Autoimmunity in ulcerative colitis (UC): a predominant colonic mucosal B cell response against human tropomyosin isoform 5
In UC but not in CC and nonâIBD controls, the increased number of IgGâproducing cells are largely committed to produce IgG against hTM5ârelated epitope(s), a putative autoantigen in UC.
Abstract
We set out to examine if the IgGâproducing 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 rectoâsigmoid and proximal colon. Twentyâthree patients with UC, eight with Crohn's colitis (CC), and 10 nonâinflammatory bowel disease (nonâIBD) 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 IgGâproducing lymphocytes was similar in UC (12%) and CC (11%), but was significantly (Pâ<â0¡0002) higher than nonâIBD controls (6%). However, in UC, but not in CC and nonâIBD, a large number of lamina propria B cells produced IgG against hTM5 (median values: UC 42%, CC 2¡5%, nonâIBD 0%). This difference in UC when compared with CC and nonâIBD was highly significant (Pâ<â0¡00001). Twentyâone of 23 (91%) patients with UC had percentage of antiâhTM5 IgGâproducing immunocytes more than 2 s.d. above the mean for nonâUC patients. In UC but not in CC and nonâIBD controls, the increased number of IgGâproducing cells are largely committed to produce IgG against hTM5ârelated epitope(s).