Human keratinocytes contain carbohydrates that are recognized by keratan sulfate-specific monoclonal antibodies

Monoclonal antibodies that recognize carbohydrate epitopes found in keratan sulfate glycosaminoglycan chains identified both intracytoplasmic and cell-surface carbohydrates of human keratinocytes. These carbohydrates were detected, using indirect immunoperoxidase methods, both in sections of paraffin-embedded tissues and in intact cultured keratinocytes. Of the seven anti-keratan sulfate monoclonal antibodies used in this study, five detected significant amounts of epitopes associated with keratinocytes. This indicates that only certain, specific types of keratan sulfate-like carbohydrates were expressed by these cells. The extent and localization of keratan sulfate-like carbohydrates appeared to be closely related to the differentiation status of cultured keratinocytes. These epitopes were very weakly expressed on surfaces of all monolayer keratinocytes, but flattened, suprabasal cells in high Ca++ cultures strongly expressed keratan sulfate-like carbohydrates on their surfaces. A much larger population of cultured keratinocytes expressed intracellular keratan sulfate-like carbohydrates identified by the same five antibodies that detected surface epitopes. In monolayer cells, keratan sulfate-like carbohydrates were predominantly found in a broad perinuclear zone. In addition, three of the five immunoreactive antibodies detected epitopes that appeared at cell boundaries, specifically at sites of close cell-to-cell contact. Thus, molecules bearing carbohydrates recognized by anti-keratan sulfate antibodies appear at developmentally important stages of keratinocyte differentiation, indicating that these carbohydrates may serve as markers for molecules important in the differentiation of human keratinocytes.