Cytokeratin and proliferative cell nuclear antigen expression in superior limbic keratoconjunctivitis.

Purpose. Superior limbic keratoconjunctivitis (SLK) is a disease of unknown etiology which showed various degrees of keratinization. The cytokeratins (CKs) are known to be the hallmark of epithelial differentiations and each CK has a characteristic distribution dependent on the type and the differentiation status of epithelium. The authors have studied the expression of cytokeratins (CKs) as well as proliferating cell nuclear antigen (PCNA) in the conjunctiva of SLK. Methods. Three superior limbic conjunctivae of patients with SLK and two normal conjunctivae were examined immunohistochemically using monoclonal antibodies against CKs and PCNA. Results. In SLK conjunctivae, increased expression of a basal cell marker (CK14) was observed throughout the epithelium. Sporadic positive staining with CK10, which is a specific marker for keratinization, was correlated to the severity of the disease. The disappearance of CK13 staining, the marker for nonkeratinized stratified epithelia, at the basal cell layer of SLK was noted. Moreover, increased expression of PCNA in SLK was observed. Conclusions. The altered expression of CKs in SLK suggests an abnormality of differentiation in the conjunctival epithelium of the disease. Upregulated proliferation of conjunctival epithelial cells may be another feature of the disease.