Cellular immunity in dogs with keratoconjunctivitis sicca before and after treatment with topical 2% cyclosporine

Peripheral cellular immunity of ten dogs with keratoconjunctivitis sicca (KCS) that had not been treated with topical corticosteroids or cyclosporine was evaluated (by use of in vitro lymphocyte proliferation assays and CD4⁺ CD8⁺ lymphocyte subset analysis) before and after 1 and 3 months of treatment with topical ocular 2% cyclosporine (CsA). In vitro lymphocyte proliferation and CD4⁺ CD8⁺ lymphocyte subset analysis was done in eight normal dogs at the 0, 1 and 3 month time periods to use for comparison. There was no significant difference in lymphocyte proliferation or numbers of CD4⁺ or CD8⁺ lymphocytes in dogs with KCS and normal dogs prior to CsA treatment. However, by 1 month's time, lymphocyte proliferation had decreased in the CsA-treated Dogs with KCS, and by 3 months there was a significant difference (P<0.0001) from the normal dogs. These results suggest that dogs with KCS may not have altered peripheral cellular immunity and that use of topical 2% cyclosporine for treatment of KCS causes a suppression of lymphocyte proliferation after 1 to 3 months of use.