Immunopathology of Prosthesis-associated Giant Papillary Conjunctivitis (P-GPC)

Abstract

Abstract: : Purpose: To examine the expression of cytokines, mast cell markers and identify functional subsets of mononuclear cell populations in the conjunctiva of patients with P-GPC. Methods: Conjunctival biopsies obtained from both eyes of 18 patients (15 males and 3 females) with P-GPC, ages between 21 to 52 years (mean=31.8+9.1 years) were examined by light microscopy and immunohistochemical techniques using the streptavidin-biotin peroxidase method. A panel of monoclonal antibodies directed against IL-2, CD1a, mast cell tryptase, mast cell chymase (MC_TC), eotaxin, TNF-alpha, IL-4, CD4, CD8 and CD138 were used after inhibition of peroxidase activity. The number of positively stained cells/mm² were counted. Results: Prosthesis-wearing time of the patients was between 4 to 160 months (median= 60 months). Total mast cell and MC_TC numbers were significantly higher in GPC specimens (p=0.049). Number of dendritic cells did not differ between eyes with GPC and normal fellow eyes. In GPC, conjunctival epithelium showed immunoreactivity for eotaxin (44%) and IL-4 (50%) more than the fellow eyes (20% and 20%, respectively) (p=0.133 and p=0.077, respectively). Eosinophil infiltration was observed in all specimens stained for eotaxin.Cytoplasmic eotaxin staining of plasma cells was consistent with the finding of higher number of plasma cells infiltrating the subepithelium in cases of high eotaxin- immunoreactivity. TNF-alpha staining was observed only in two biopsies from GPC patients.When compared with the normal fellow eyes, the numbers of CD4⁺ and CD8⁺ T lymphocytes were higher in GPC eyes.Mononuclear cells were stained for IL-2 and IL-4. Goblet cells were more common in GPC eyes than the fellow eyes (p=0.019). Conclusions: Increased number of connective tissue type mast cells, eosinophils, plasma cells and T cells play role in the pathogenesis of P-GPC, a rather complicated allergic reaction. Eotaxin is crucial for chemotaxis of eosinophils into the area of allergic inflammation and shown to be expressed by the epithelial and the plasma cells. The high number of CD8⁺ lymhocytes points to the role of delayed hypersensitivity reaction in P-GPC.

Keywords: conjunctivitis • immunohistochemistry • cytokines/chemokines