NORADRENERGIC AND PEPTIDERGIC INNERVATION OF LYMPHOID ORGANS IN THE BELUGA, DELPHINAPTERUS-LEUCAS - AN ANATOMICAL LINK BETWEEN THE NERVOUS AND IMMUNE-SYSTEMS

The presence of peptidergic and noradrenergic sympathetic nerve fibers in specific compartments of both primary and secondary lymphoid organ s of the rodent is well established. These nerve fibers directly conta ct lymphocytes and macrophages, as well as vascular and trabecular smo oth muscle. We investigated the noradrenergic and neuropeptide-Y inner vation of lymphoid organs in the cetacean, Delphinapterus leucas (belu ga whale). The spleen, thymus, tonsil, gut-associated lymphoid tissue, and assorted lymph nodes were collected from five belugas, obtained d uring sanctioned hunts, and processed for catecholamine fluorescence h istochemistry and for tyrosine hydroxylase and neuropeptide-Y immunocy tochemistry. Innervation studies revealed fluorescent nerve fibers, ty rosine hydroxylase, and neuropeptide-Y positive nerve fibers in parenc hymal lymphoid compartments, where they were closely associated with c ells of the immune system, and in vascular and trabecular compartments . In lymphoid zones, tyrosine hydroxylase and neuropeptide-Y positive nerve fibers were observed in the periarteriolar lymphatic sheath and marginal zone of the spleen; in the outermost portion of the cortex, t he corticomedullary zone, and medulla of the lymph nodes; in the paraf ollicular zones, and diffuse lymphocyte layer below the epithelium of the tonsil; in the outermost portion of some thymic lobules; and in th e lamina propria of the gut. These findings are similar to those descr ibed for other mammals and substantiate an anatomical link between the nervous and immune systems in the beluga, whereby central nervous sys tem activity may influence autonomic outflow to lymphoid organs and ef fect immunologic reactivity. (C) 1994 Wiley-Liss, Inc.