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Abstract
PURPOSE: In lacrimal glands, cell-cell interactions control the localization of lymphocyte populations that play a role in immune defense at the ocular surface. This study describes lymphocyte adhesive interactions with cultured lacrimal gland acinar epithelial cells. METHODS: Primary cultures of lacrimal gland epithelial cells were used as targets for in vitro lymphocyte binding assays. The relative adherence of lymphocyte populations was determined. Various physiologically active agents and putative ligand analogs were tested for their effect in the binding assay. RESULTS: Thoracic duct lymphocytes (TDL) bound to cultured lacrimal acinar epithelial cells in greater numbers than did thymocytes (54 cells/mm2 versus 8 cells/mm2). B cells showed preferential adherence compared with T cells (75% sIg+, 14% W3/13+). Thoracic duct lymphocyte binding required intact metabolic and membrane-cytoskeletal function and was inhibited by treating the lymphocytes with sodium azide, formaldehyde, or cytochalasin B (23%, 12%, and 10% of control binding, respectively). Further, adherence was dependent on divalent cations. Ethylenediaminetetraacetic acid-mediated inhibition (42% of untreated) was restored by replacing calcium (89%) but not magnesium (41%). Lymphocyte adherence was inhibited in the presence of fucoidin or phosphomannan polysaccharides (36% and 48% of control binding, respectively). Fibronectin peptides, which are involved in certain types of integrin-mediated adherence, had no effect in this system. Lacrimal culture supernatants contained a factor that was inhibitory for TDL adherence (more than 50% inhibition when concentrated 5 or 10 times). CONCLUSIONS: Thoracic duct lymphocyte adherence to cultured lacrimal gland acinar epithelial cells shows good correlation with previously reported adherence to lacrimal gland frozen sections. Further, lacrimal cell culture supernatants contain soluble factors that inhibit TDL adherence to epithelial cells. These findings suggest that the lacrimal molecules involved in lymphocyte localization are shed and that lacrimal epithelial cell cultures will be useful for ligand isolation and characterization.