Infiltration of CD8+ T cells containing RANTES/CCL5+ cytoplasmic granules in actively inflammatory lesions of human chronic gastritis

Abstract

Chronic gastritis is frequently associated with infection of Helicobacter pylori and characterized by tissue infiltration of neutrophils, lymphocytes, and plasma cells. To address the mechanism of lymphocyte infiltration in chronic gastritis, we examined the expression of chemokines and their receptors using frozen sections of chronic gastritis, obtained from 23 patients who underwent gastrectomy for gastric cancer. By immunohistochemistry, lymphocytes in inflamed gastric mucosa expressed CCR5 abundantly, CXCR3 less frequently, and CCR4 sparsely. The numbers of CCR5+ cells, which were composed of mainly CD8+ and partly CD4+ T cells, were positively correlated with the degree of neutrophil infiltration, and decreased in areas with intestinal metaplasia or mucosal atrophy. RANTES/CCL5, one of the ligands of CCR5, was localized mainly in CD8+ and partly CD4+ T cells with a characteristic dotted pattern, and such lymphocytes were most densely distributed around the neck region of gastric glands. In situ hybridization confirmed the expression of CCL5 mRNA in these cells, and immunoelectron microscopy revealed localization of CCL5 in the membrane-bound granules, which most probably corresponded to the cytolytic granules of cytotoxic T cells. The numbers of CCL5+ lymphocytes showed a close correlation with the degree of neutrophil infiltration and markedly decreased in intestinal metaplasia. In conclusion, our data suggest that, together with neutrophils, CCL5+ T cells, presumably activated cytotoxic T cells, would play important roles in the active inflammatory process of chronic gastritis. Our data also suggest a self-recruiting mechanism involving CCR5 and CCL5 for tissue accumulation of such T cells.