Cellular and tissue architecture of conjunctival membranes in epidemic keratoconjunctivitis

Purpose: Conjunctival membranes are differentiated from pseudomembranes by bleeding on removal. The authors sought to study the cellular constituents and extracellular structure of formed conjunctival exudates in epidemic keratoconjunctivitis (EKC), and to determine whether these represent true conjunctival membranes. Methods: Formed conjunctival exudates harvested from 2 patients with EKC were studied by immunohistochemistry. Adenoviral infection was evaluated by PCR. Results: Each patient's tears were PCR positive for adenovirus, but not HSV-I. Both conjunctival specimens contained a fibrinous stroma richly populated with cells positive for CD4, CD8, CD20, CD68, myeloperoxidase, and fascin. Both specimens also contained cells positive for CD31 and Tie-2, and demonstrated expression of transforming growth factor-β and vascular endothelial growth factor. Conclusions: Conjunctival exudates in EKC contain a range of leukocytes representing both innate and acquired immune responses, along with angiogenic factors and proliferating endothelial cells. Therefore, true conjunctival membranes can and do form in EKC.