Immunohistochemistry of the inflammatory response in Propionibacterium acnes endophthalmitis.

Specimens were obtained from two patients with culture-proven Propionibacterium acnes endophthalmitis who had undergone vitrectomy. Wright's and Giemsa stains were performed using cytospin preparations of the dilute vitreous and revealed a predominance of polymorphonuclear leukocytes (80% to 90%). The remaining inflammatory cells in the vitreous were mostly macrophages (10% to 15%); very few lymphocytes were present (less than 5%). Immunohistochemical studies using monoclonal antibodies confirmed the paucity of lymphocytes. Most lymphocytes were CD4+ helper/inducer T cells. Almost no CD8+ suppressor/cytotoxic T lymphocytes or B lymphocytes were found. The inflammatory response in these two patients is most characteristic of acute inflammation and consistent with an underlying bacterial infection, despite a clinical picture of persistent, low-grade inflammation. Infection with P acnes has been shown to inhibit CD8+ T cells and may play a role in the persistent inflammation in cases of P acnes endophthalmitis.