CATECHOLAMINE INFLUENCES AND SYMPATHETIC NEURAL MODULATION OF IMMUNE RESPONSIVENESS

Primary and secondary lymphoid organs are innervated extensively by no radrenergic sympathetic nerve fibers. Lymphocytes, macrophages, and ot her cells of the immune system bear functional adrenoreceptors. Norepi nephrine fulfills criteria for neurotransmission with cells of the imm une system as targets. In vitro, adrenergic agonists can modulate all aspects of an immune response (initiative, proliferative, and effector phases), altering such functions as cytokine production, lymphocyte p roliferation, and antibody secretion. In vivo, chemical sympathectomy suppresses cell-mediated (T helper-1) responses, and may enhance antib ody (T helper-2) responses. Noradrenergic innervation of spleen and ly mph nodes is diminished progressively during aging, a time when cell-m ediated immune function also is suppressed. In animal models of autoim mune disease, sympathetic innervation is reduced prior to onset of dis ease symptoms, and chemical sympathectomy can exacerbate disease sever ity. These findings illustrate the importance of the sympathetic nervo us system in modulating immune function under normal and disease state s.