Purpose: To investigate feasibility and potential uses of flow cytometry in impression cytology as a new procedure to assess and quantify conjunctival inflammation.
Methods: Specimens for cytology were collected by impression from 30 patients with various chronic ocular surface disorders and from 10 normal subjects. Two specimens were obtained in each eye: One was transferred onto a glass slide and processed by immunofluorescence with antibodies to human leukocyte antigen (HLA)-DR antigens; cells from the other were suspended in phosphate-buffered saline for flow cytometry. Monoclonal antibodies to HLA-DR antigens and CD23, the low affinity receptor to immunoglobulin E, were used.
Results: Abnormal expression of HLA-DR and CD23 by conjunctival cells was found in 13 of 18 dry eyes and in 20 of 22 eyes with chronic conjunctivitis, whereas specimens remained almost negative (less than 10% of cells were positive) in normal eyes. Percentages of positive cells ranged between 20% and 98% of all conjunctival cells. Correlation between the two methods, immunocytology and flow cytometry, was highly significant (coefficient of correlation 0.77, P = 0.0001). Moreover, HLA-DR positivity, at its strongest intensity, was observed in a minority of cells (1% to 12%), most of which were resident class II-expressing dendritic cells. Percentages of those cells expressing high levels of HLA-DR were 3 +/- 1.2% in normal eyes, 5.8 +/- 4% in dry eyes (P = 0.05), and 5.9 +/- 3.5% in eyes with chronic conjunctivitis (P = 0.02).
Conclusions: Results of this preliminary study confirm that conjunctival epithelial cells may abnormally express inflammatory markers in chronic ocular surface disorders. Development of flow cytometry in analysis of cytologic specimens provides a new, sensitive, and objective tool for exploring conjunctival pathology.