FLOW-CYTOMETRY IN IMPRESSION CYTOLOGY SPECIMENS - A NEW METHOD FOR EVALUATION OF CONJUNCTIVAL INFLAMMATION

Purpose. To investigate feasibility and potential uses of flow cytomet ry in impression cytology as a new procedure to assess and quantify co njunctival inflammation. Methods. Specimens for cytology were collecte d by impression from 30 patients with various chronic ocular surface d isorders and from 10 normal subjects. Two specimens were obtained in e ach eye: One was transferred onto a glass slide and processed by immun ofluorescence with antibodies to human leukocyte antigen (HLA)-DR anti gens; 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. A bnormal 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 we re positive) in normal eyes. Percentages of positive cells ranged betw een 20% and 98% of all conjunctival cells. Correlation between the two methods, immunocytology and flow cytometry, was highly significant (c oefficient of correlation 0.77, P = 0.0001). Moreover, HLA-DR positivi ty, at its strongest intensity, was observed in a minority of cells (1 % to 12%), most of which were resident class II-expressing dendritic c ells. 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 epithelia l cells may abnormally express inflammatory markers in chronic ocular surface disorders. Development of flow cytometry in analysis of cytolo gic specimens provides a new, sensitive, and objective tool for explor ing conjunctival pathology.