Innervation of mouse lymph nodes: Nerve endings on muscular vessels and reticular cells

Abstract

Lymph node nerve endings have been studied in 1- to 48-day-old mice. Serial sections of Epon-embedded lymph nodes were observed under the electron microscope to find the nerve endings. Most lymph node nerve fibers finally reach the smooth muscle cells of arterioles and muscular venules. Both kinds of vascular endings are similar, although endings are less numerous on venules. Nerve endings consist of one or more nerve processes surrounded by a usually incomplete Schwann cell sheath; frequently, axons show wide areas directly facing the muscle cells. The distance between such a naked axon and a myocyte ranges from 100 to 800 nm. Small granulated and clear vesicles are especially abundant in varicosities of nerve processes that are located very close to muscle cells. Nerve endings of lymph node vasculature probably correspond to vasomotor sympathetic adrenergic endings, regulating the degree of contraction of vessels which have a muscular layer. Other kinds of nerve endings also exist in lymph nodes: some axons appear free in the stroma and contact the surfaces of reticular cells; the latter also extend delicate cytoplasmic processes that surround the axons. The functional significance of nerve cell-reticular cell contacts is unknown.

Ultrastructural quantitative analysis of the innervation of axillary lymph nodes of the rat after antigenic stimulation

“…For the lymph node it has been postulated that reticular cells are motile (Muller-Hermelink et al, 1981;Tykocinski et al, 1983). In addition t o our reports, one further group has reported close associations betwen reticular cells and axonal varicosities (Villardo et al, 1986). Claims have been made that the reticular cells of the medulla and the follicular dendritic cells have a common origin (Groscurth, 1980;Heusermann et al, 1980), and reaction of both cell types to a common antibody has been reported (Van Vliet et al, 1986).…”

Without nerves, immunology remains incomplete –in vivo veritas

“…Similar conclusions were arrived at in the late 1980s, when electron microscopy enabled the definition of partially myelinated axons entering the node, as well as potential sensory nerve terminals associated principally with the vasculature 37 but also branching into cortical and paracortical regions, terminating among lymphocytes. 38,39 Dense plexuses of adrenergic fibres in association with blood vessels and the surrounding periarterial lymphatic sheath in lymph nodes have been demonstrated, as have occasional fibres with no apparent vascular association in the cortical, paracortical and medullary regions of lymph nodes. 40 Staining for a number of peptide mediators has proven positive, showing potential co-localization between SP and CGRP, among others, reflecting the association seen in the skin.…”

The β2-adrenergic receptor controls inflammation by driving rapid IL-10 secretion

“…In addition, the immune system is also under direct control by the central nervous system. Early studies demonstrated that both primary and secondary lymphoid tissue s are innervated by post-ganglionic sympathetic neurons that secrete NE as the primary neurotransmitter 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 Likewise, immune cells express adrenergic receptors, which bind both epinephrine (E) and NE, giving the immune system the ability to directly respond to signals from the autonomic nervous system. E is primarily secreted by the chromaffin cells within the adrenal gland and exerting systemic effects, whereas NE is secreted predominantly by sympathetic nerves that terminate locally within peripheral organs.…”