FACTORS CONTROLLING T-CELL MIGRATION ACROSS RAT CEREBRAL ENDOTHELIUM IN-VITRO

The migration of lymphocytes through primary cultures of rat brain mic rovascular endothelial cell monolayers was examined in vitro by time-l apse videomicroscopy. Antigen-specific T cell line migration was depen dent on the duration of culture (post-antigen stimulation) with exogen ous interleukin-2 (IL-2). Peak migration (approximately 50% of T-cells during the 4 h migration assay) occurred after 4 days of culture with IL-2 but did not coincide with maximal expression of LFA-1, VLA-4 or the IL-2 receptor. On unstimulated endothelin antibody blockade of LFA -1 or ICAM-1 inhibited T-cell line migration to 8.0% and 6.5% of contr ol values, respectively, whereas blocking VLA-4 and VCAM-1 had no effe ct. On IL-beta activated endothelium blocking LFA-1 and ICAM-1 was les s effective (24.9% and 27.3% of control values, respectively) and bloc kade of VLA-4 and VCAM-1 brought about a reduction to 63.0% and 68.3% of controls respectively. Inhibition of IL-2-dependent proliferation w ith an IL-2 receptor blocking antibody also significantly inhibited T- cell migration to 22.2% of controls. Peripheral lymph node (PLN) lymph ocytes could also be induced to migrate through untreated cerebral end othelial cell monolayers by cross-linking CD3 which was also time and IL-2-dependent with maximal migration (22.7%) occurring after three da ys in the presence of exogenous IL-2. Blocking LFA-1 or ICAM-1 resulte d in a significant reduction in migration across IL-1 beta-activated e ndothelial cells to 17.4% and 20.9% of control values respectively alt hough blocking the VLA-4/VCAM-1 interaction had no significant effect. Activation of PLN lymphocytes with concanavalin A for up to 5 days di d not induce migration bur when left in contact with the endothelial m onolayer for 24 h migration reached 31.0%. These studies indicate that T-cells require a combination of signals to trigger the migratory phe notype which is necessary to enable them to penetrate the blood-brain barrier.