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Immunohistochemistry of the inflammatory response in Propionibacterium acnes endophthalmitis
S M Whitcup1, R Belfort, M D de Smet
1Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Md. 20892.
Abstract:
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.
Insights
Propionibacterium acnes endophthalmitis involves acute inflammation with abundant polymorphonuclear leukocytes. This bacterial infection may cause persistent inflammation by inhibiting CD8+ T cells.
Area of Science:
- Ophthalmology
- Microbiology
- Immunology
Background:
- Propionibacterium acnes (P. acnes) is a bacterium known to cause endophthalmitis, an inflammation of the inner eye.
- Understanding the host's inflammatory response is crucial for managing P. acnes endophthalmitis, especially in persistent cases.
Observation:
- Vitreous samples from two patients with P. acnes endophthalmitis were analyzed.
- Cytospin preparations revealed a predominance of polymorphonuclear leukocytes (80-90%) and macrophages (10-15%).
- Lymphocytes were notably scarce (<5%), with immunohistochemistry confirming a lack of CD8+ T cells and B lymphocytes, while CD4+ T cells were present.
Findings:
- The inflammatory infiltrate is characteristic of acute bacterial infection, despite a clinical presentation of chronic, low-grade inflammation.
- The scarcity of CD8+ T cells suggests a potential immune evasion mechanism by P. acnes.
- The observed immune cell profile points towards a specific host response to P. acnes infection.
Implications:
- P. acnes may actively suppress CD8+ T cell responses, contributing to the persistence of endophthalmitis.
- This immune modulation by P. acnes could be a key factor in the chronicity and difficulty in treating these infections.
- Further research into P. acnes immune interactions may reveal novel therapeutic targets for endophthalmitis.