A patient with a history of cold sores on the lip develops a branching, dendritic corneal ulcer with terminal bulbs on fluorescein staining. The keratocytes show multinucleated giant cells on impression cytology. Herpes simplex stromal keratitis is subsequently diagnosed. Which immunological mechanism is primarily responsible for stromal destruction in HSK?
- A Direct cytopathic effect of HSV-1 replicating in stromal keratocytes
- B IgE-mediated mast cell degranulation in the corneal stroma
- C Complement-mediated lysis of corneal endothelial cells by anti-HSV antibodies
- D CD4+ T-cell mediated delayed-type hypersensitivity response to viral antigens in stroma ✓
Explanation
Herpes simplex stromal keratitis (necrotizing and non-necrotizing disciform forms) is primarily an immunopathological process rather than direct viral cytopathic effect. After epithelial infection, viral antigens (particularly HSV glycoproteins) are deposited in the stroma. CD4+ T-lymphocytes mediate a delayed-type hypersensitivity (Type IV) response against these antigens, releasing cytokines (IFN-γ, TNF-α) that recruit neutrophils and macrophages, causing stromal opacification, neovascularization, and ulceration. This explains why immunosuppressive topical steroids (with antiviral cover) are therapeutic in stromal keratitis.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.