Lack of T cell proliferation without induction of nonresponsiveness after antigen presentation by endothelial cells.

BACKGROUND: After priming or reactivation in lymph nodes, T cells recirculate to sites of inflammation, and enter tissues by migrating across activated endothelium. Given that activated endothelial and tissue parenchymal cells express both class I and class II MHC molecules, it is probable that transmigrating T cells encounter cognate antigen on endothelial cells, and on tissue parenchymal cells once they have entered the tissue. METHODS: In this study the consequences of antigen presentation by endothelial and epithelial cells to human CD4+ T cell clones were analyzed and compared by a two-step culture system. RESULTS: T cell clones that required B7-mediated costimulation to be activated were found not to be able to proliferate to antigen presented by either endothelial or epithelial cells, unless trans-costimulation was provided by the addition of B7-transfected cells in the cultures. Furthermore, antigen presentation by epithelial cells induced nonresponsiveness in the T cell clones. In contrast, after cognate recognition on endothelial cells, the ability of the T cell clones to proliferate to a subsequent rechallenge with antigen presented on a specialized APC was unaffected. CONCLUSIONS: These data suggest that endothelial cells have unique properties as antigen-presenting cells, in that they do not influence the subsequent reactivity of cognate T cells.