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A Pyrrhic Victory: The PMN Response to Ocular Bacterial Infections
Erin T Livingston1, Md Huzzatul Mursalin1, Michelle C Callegan1,2,3,4
1Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
Abstract:
Some tissues of the eye are susceptible to damage due to their exposure to the outside environment and inability to regenerate. Immune privilege, although beneficial to the eye in terms of homeostasis and protection, can be harmful when breached or when an aberrant response occurs in the face of challenge. In this review, we highlight the role of the PMN (polymorphonuclear leukocyte) in different bacterial ocular infections that invade the immune privileged eye at the anterior and posterior segments: keratitis, conjunctivitis, uveitis, and endophthalmitis. Interestingly, the PMN response from the host seems to be necessary for pathogen clearance in ocular disease, but the inflammatory response can also be detrimental to vision retention. This "Pyrrhic Victory" scenario is explored in each type of ocular infection, with details on PMN recruitment and response at the site of ocular infection. In addition, we emphasize the differences in PMN responses between each ocular disease and its most common corresponding bacterial pathogen. The in vitro and animal models used to identify PMN responses, such as recruitment, phagocytosis, degranulation, and NETosis, are also outlined in each ocular infection. This detailed study of the ocular acute immune response to infection could provide novel therapeutic strategies for blinding diseases, provide more general information on ocular PMN responses, and reveal areas of bacterial ocular infection research that lack PMN response studies.
Insights
Polymorphonuclear leukocytes (PMNs) are crucial for clearing bacterial eye infections but can also cause vision loss. Understanding PMN roles in ocular diseases like keratitis and endophthalmitis may lead to new treatments.
Area of Science:
- Ophthalmology
- Immunology
- Microbiology
Background:
- The eye's immune privilege protects it but can complicate infections.
- Bacterial pathogens can invade anterior and posterior eye segments, causing serious conditions like keratitis, conjunctivitis, uveitis, and endophthalmitis.
Purpose of the Study:
- To review the critical role of polymorphonuclear leukocytes (PMNs) in bacterial ocular infections.
- To explore the dual nature of PMN responses, essential for pathogen clearance yet potentially damaging to vision.
- To compare PMN responses across different ocular infections and their causative bacteria.
Main Methods:
- Review of existing literature on bacterial ocular infections.
- Analysis of PMN recruitment, phagocytosis, degranulation, and NETosis in ocular disease models (in vitro and animal).
- Comparison of PMN responses specific to distinct ocular infections and pathogens.
Main Results:
- PMN response is vital for clearing bacterial eye infections but can lead to detrimental inflammation and vision loss.
- Significant differences exist in PMN responses depending on the specific ocular infection and bacterial pathogen involved.
- Studies utilize in vitro and animal models to investigate PMN functions like recruitment and NETosis in ocular infections.
Conclusions:
- Understanding the "Pyrrhic Victory" of PMN responses in ocular infections is key to developing new therapies.
- Further research into PMN behavior in specific bacterial eye diseases can inform treatment strategies for blinding conditions.
- Identifying gaps in current research on PMN responses in bacterial ocular infections is crucial for future studies.
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