Background/aims To examine the characteristics of infiltrating cells in conjunctival tissues adjacent to the peripheral corneal ulcers of Mooren's ulcer.

Methods This study involved four eyes of four patients with Mooren's ulcer and who were considered to be in need of surgical treatment. The patients’ resected conjunctival tissues were embedded and frozen. The tissue sections were then subjected to H&E and immunohistochemical staining. The stained sections were observed and the characteristics of the infiltrating cells in the conjunctival tissues were pathologically examined.

Results In all patients, infiltration of inflammatory cells was observed in the submucosal connective tissue of the conjunctiva. Immunohistochemical analysis revealed inflammatory cell infiltration into the submucosal layer of the conjunctiva that was mainly composed of CD3-positive and CD45RO-positive cells. Some of these cells also showed positive reactivity with CD4, yet very few cells showed positive reactivity with CD8. In addition, infiltration of the cells indicating CD68 positivity was frequent in a few cases.

Conclusions In the four Mooren's ulcer cases, infiltrating cells in the submucosa of the conjunctival tissues adjacent to the ulcerative cornea were found to be mainly composed of helper T lymphocytes and macrophages. Our results show that helper T cells and macrophages contribute to the pathogenesis of Mooren's ulcer.