Human T cell clones express functional homing receptors required for normal lymphocyte trafficking.

To function efficiently in vivo, lymphocytes must circulate from the blood into lymphoid tissues and other sites of immune reaction. Herein, we show that human cytotoxic and helper T cell clones and lines, maintained in vitro with IL-2, express the functional capacity to recognize and bind to high endothelial venules (HEV), a capacity essential for lymphocyte exit from the blood, and hence for normal lymphocyte trafficking. The expression of functional homing receptors distinguishes human T cell clones from their murine counterparts, which uniformly lack receptors for HEV and are unable to migrate normally from the blood in vivo. The results raise the possibility that human T cell clones may be more effective in mediating in vivo immune responses than is suggested by murine models.