T lymphocytes-blood retina barrier cells interactions in vitro : the role of adhesion molecules and inflammatory mediators
The BRB consists of both capillary endothelial cells (REC) and retinal pigment epithelial cells (RPE). Both cell types have been suggested as potential activators of circulating T cells. In this study, an in vitro model using cultured rat REC and syngeneic T cells was developed. Furthermore RPE and for the purpose of comparative studies, AEC were also successfully cultured. It was demonstrated that activation of T lymphocyte LFA-1 is a critical event governing the adhesion of T cells to RPE and REC as IFN-γ induced up-regulation of RPE and REC ICAM-1 expression did not increase binding of resting T lymphocytes. The enhanced adhesion of activated lymphocytes (but not resting lymphocytes) to normal and IFN-γ treated RPE and REC was inhibited by LFA-1 mAb and to a lesser extent by ICAM-1 mAb but not OX34 (CD2). Treatment of lymphocytes with the anti-VLA-4 mAb resulted in differential effects on binding to AEC and REC. MAb to VLA-4 significantly blocked enhanced adhesion of activated T cells to AEC but not to REC. The results also demonstrated that VLA-4 mAb significantly inhibited unactivated T cell binding to IFNγ+TNFα+LPS stimulated AEC but not REC, suggesting that VLA-4 may also function in an activation-independent manner. It was shown that activation of T cells can enhance their migratory activity across cultured REC monolayers. Migration was decreased by both adhesion receptor-dependent mechanisms i.e., mAb to LFA-1 (but not ICAM-1) and adhesion receptor-independent mechanisms by means of PGE2. The results of this thesis have shown that activation of LFA-1 is required for functioning of the LFA-1/ICAM-1-mediated lymphocyte adhesion and migration. In addition to the role of adhesion molecules, inflammatory mediator PGE2, but not NOo, was found to be important in regulation of T cell adhesion and migration across REC.