Production of immunoglobulin G and G1 antibodies to cytoskeletal protein by lamina propria cells in ulcerative colitis

Background & Aims: Recent studies suggest an autoantigenic role for tropomyosin-related protein(s) in ulcerative colitis (UC). This study examined whether immunoglobulin G and G1 subclass antibodies against tropomyosins are produced spontaneously by the lamina propria mononuclear cells (LPMCs) that infiltrate the inflamed UC tissue. Methods: LPMCs were isolated from colonic biopsy specimens from 29 patients with UC, 15 with colonic Crohn's disease (CD), and 13 with non-inflammatory bowel disease (IBD). The autologous peripheral blood mononuclear cells (PBMCs) were obtained. Cells were cultured in vitro and unstimulated for 10 days. Spontaneous production of immunoglobulin G and G1 antibodies against tropomyosins was measured by enzyme-linked immunosorbent assays using highly enriched tropomyosins from skeletal muscle and colonic mucosa. Results: The total immunoglobulin G produced by LPMCs from both patients with UC and CD was comparable but higher than from patients with non-IBD ( P < 0.05). However, immunoglobulin G antibodies to tropomyosins were higher in patients with UC than in patients with CD ( P < 0.04) and non-IBD ( P < 0.02). LPMCs from patients with symptomatic UC produced higher immunoglobulin G antibodies to tropomyosins than patients with UC in remission ( P < 0.03), symptomatic CD ( P < 0.04), and non-IBD ( P < 0.02). Immunoglobulin G antibodies to tropomyosins predominantly belonged to immunoglobulin G1 subclass. The autologous PBMCs showed comparable results. Conclusions: Immunoglobulin G antibodies predominantly belonging to immunoglobulin G1 subclass and reactive against tropomyosin-related protein(s) are spontaneously produced by LPMCs from the colonic mucosa in patients with UC.