Accumulation of mast cells and macrophages in focal active gastritis of patients with Crohn's disease.

Background/aims: Recent studies have shown that focal active gastritis seems to be the typical gastric pathology in Crohn's disease. The aim of this study was to compare the incidence of focal active gastritis, Helicobacter pylori infection and distribution of gastric mast cells and macrophages in patients with Crohn's disease, ulcerative colitis and H. pylori gastritis without inflammatory bowel disease.

Methodology: Patients with histologically confirmed Crohn's disease (n = 25) or ulcerative colitis (n = 25) and control patients without inflammatory bowel disease (n = 25) were included in this study. Biopsy specimens were obtained from the antrum and corpus of each patient, and stained with hematoxylin and eosin and immunostained using antibodies to tryptase (AA1) and CD68. The number of mast cells and macrophages located in the lamina propria was determined.

Results: Focal active gastritis was detected in 54% of H. pylori-negative patients with Crohn's disease, but it was not found in patients with ulcerative colitis nor in the control group. The density of mast cells and macrophages in the lamina propria of H. pylori-positive patients was significantly higher than in H. pylori-negative patients in all groups. In the Crohn's disease group, the number of mast cells (antrum; 83 +/- 11, body; 89 +/- 11/mm2) and macrophages (antrum; 94 +/- 22, body; 92 +/- 17/mm2) in the lamina propria of H. pylori-negative patients with focal active gastritis was halfway between that in H. pylori-positive and H. pylori-negative patients. In focal active gastritis, mast cells accumulated at the border of focal active gastritis, whereas macrophages accumulated in the center of such lesions.

Conclusions: Our findings indicated that the diagnosis of focal active gastritis, using immunostain for mast cells and macrophages, is the histological hallmark of gastric Crohn's disease. Macrophages might be associated with the formation of focal active gastritis in patients with Crohn's disease.