Control of lymphocyte egress from lymph nodes through ß2-adrenergic receptors.

Lymphocyte recirculation through secondary lymphoid organs is essential for immunosurveillance and lymphocyte effector functions. Here, we show that signals through ß2-adrenergic receptors (ß2ARs) expressed on lymphocytes are involved in the control of lymphocyte dynamics by altering the responsiveness of chemoattractant receptors. Agonist stimulation of lymphocyte ß2ARs inhibited egress of lymphocytes from lymph nodes (LNs) and rapidly produced lymphopenia in mice. Physiological inputs from adrenergic nerves contributed to retention of lymphocytes within LNs and homeostasis of their distribution among lymphoid tissues. ß2ARs physically interacted with CCR7 and CXCR4, chemokine receptors promoting lymphocyte retention in LNs. Activation of ß2ARs enhanced retention-promoting signals through CCR7 and CXCR4, and consequently inhibited lymphocyte egress from LNs. In models of T cell-mediated inflammatory diseases, ß2AR-mediated signals inhibited LN egress of antigen-primed T cells and reduced their recruitment into peripheral tissues. Thus, this study reveals a novel mechanism for controlling lymphocyte trafficking and provides additional insights into immune regulation by the nervous system.