Lymphocyte Migration across the Anterior and Posterior Blood–Retinal Barrierin Vitro

The migration of lymphocytes through monolayers of rat retinal pigment epithelium (RPE) and retinal vascular endothelium, which form the posterior and anterior blood–retinal barrier (BRB) respectively, was investigatedin vitro.After a 4-hr assay the migration of untreated peripheral lymph node (PLN) cells through RPE monolayers was negligible (<1%) with only a small increase found after activation of the PLN cells with concanavalin A or by cross-linking CD3. Activation of the RPE with IFN-γ augmented migration with maximal PLN cell migration being achieved with a combination of CD3 cross-linking and IFN-γ activation (17% migration). The highest level of lymphocyte migration was observed with three CD4+antigen-specific T cell lines specific for purified protein derivative (PPD; 33% migration), ovalbumin (OA; 31%), and S-antigen (S-Ag; 57%). Migration of both untreated and Con A-activated PLN cells through retinal endothelial cells (EC) from PVG rats was negligible, whereas the migration of the antigen-specific T cell lines was 23, 29, and 23% for PPD, OA, and S-Ag lines, respectively. Migration of these cell lines through retinal endothelium derived from Lewis rats was significantly greater (44% for PPD, 39% for OA, and 39% for S-Ag) which corresponded with a greater expression of ICAM-1 on the EC.