Intrinsic factor Recognition Promotes Th17/Th1 Autoimmune Gastric Inflammation in Patients with Pernicious Anemia

Abstract

Abstract The intrinsic factor (IF) is the major humoral autoantigen in pernicious anemia (PA)/autoimmune gastritis. Although many studies have examined the autoantibody response to intrinsic factor and H+,K+-ATPase, no information is available on possible pathogenic mechanisms mediated by IF-specific gastric T cells. The aim of this study was to investigate IF-specific T cells in the gastric mucosa of PA patients and define their functional properties. In vivo-activated T cells from the infiltrates of the gastric mucosa of PA patients were isolated and cloned. We investigated the ability of the gastric T-cell clones to proliferate and produce cytokines in response to IF, as well as their helper function for antibody production and their cytolytic potential. For the first time we provide evidence that gastric mucosa of PA patients harbour a high proportion (20%) of autoreactive activated CD4+ T-cell clones that specifically recognize IF. Most of these clones (94%) showed a Th17 or Th1 profile. Virtually all IF-specific clones produced TNFα, IL-21 and provided substantial help for B-cell immunoglobulin production. Most mucosa-derived IF-specific T-cell clones expressed perforin-mediated cytotoxicity and induced Fas-Fas ligand-mediated apoptosis in target cells. Altogether, our results suggest that chronic autoantigen-induced T cell– dependent B-cell activation is responsible for the local synthesis of IF autoantibodies found in the sera and indicate that activation of IF-specific Th17 and Th1 T cells in the gastric mucosa represent a key effector mechanism in PA suggesting that the Th17/Th1 pathway may represent a novel target for the prevention and treatment of the disease.