Objective: To characterize chemokine receptor CCR5 expression on the conjunctival epithelium in dry eye syndromes.
Methods: Conjunctival impression cytology samples were obtained from normal subjects (n = 15) and patients with dry eye syndrome (n = 45). Cells were harvested from impression cytology samples, and flow cytometry was performed to quantitatively analyze the cell surface expression of chemokine receptor CCR5. Characterization of CCR5-positive cells was done by 2-color flow cytometry using fluorescein-conjugated anti-CCR5 and phycoerythrin-conjugated anti-CD45 antibodies (where CD45 is a marker for bone marrow-derived cells). To study CCR5 messenger RNA transcripts, real-time polymerase chain reaction was done on RNA isolated from the impression cytology samples of normal subjects (n = 5) and patients with dry eye syndrome (n = 14).
Results: We found significant up-regulation in cell surface expression of CCR5 in patients with both aqueous tear-deficient and evaporative forms of dry eye syndrome (P<.001). The real-time polymerase chain reaction results (for messenger RNA) corroborated the flow cytometry data (for protein). The majority of the cells expressing CCR5 were non-bone marrow-derived resident epithelial cells of the conjunctiva.
Conclusion: Our findings suggest that CCR5 up-regulation is significantly associated with dry eye syndrome-associated ocular surface disease. Clinical Relevance Chemokine receptor CCR5 or its ligands may serve as useful targets for modulation of tissue immunoinflammatory responses in dry eye syndromes.