Neuropeptide-Y innervation of the rat spleen: another potential immunomodulatory neuropeptide

Disrupted autonomic pathways in spinal cord injury: Implications for the immune regulation

Spinal Cord Injury (SCI) disrupts critical autonomic pathways responsible for the regulation of the immune function. Consequently, individuals with SCI often exhibit a spectrum of immune dysfunctions ranging from the development of damaging pro-inflammatory responses to severe immunosuppression. Thus, it is imperative to gain a more comprehensive understanding of the extent and mechanisms through which SCI-induced autonomic dysfunction influences the immune response. In this review, we provide an overview of the anatomical organization and physiology of the autonomic nervous system (ANS), elucidating how SCI impacts its function, with a particular focus on lymphoid organs and immune activity. We highlight recent advances in understanding how intraspinal plasticity that follows SCI may contribute to aberrant autonomic activity in lymphoid organs. Additionally, we discuss how sympathetic mediators released by these neuron terminals affect immune cell function. Finally, we discuss emerging innovative technologies and potential clinical interventions targeting the ANS as a strategy to restore the normal regulation of the immune response in individuals with SCI.

Neural control of the spleen as an effector of immune responses to inflammation: mechanisms and treatments

Immune system responses are a vital defense mechanism against pathogens. Inflammatory mediators finely regulate complex inflammatory responses from initiation to resolution. However, in certain conditions, the inflammation is initiated and amplified, but not resolved. Understanding the biological mechanisms underlying the regulation of the immune response is critical for developing therapeutic alternatives, including pharmaceuticals and bioelectronic tools. The spleen is an important immune effector organ since it orchestrates innate and adaptive immune responses such as pathogen clearance, cytokine production, and differentiation of cells, therefore playing a modulatory role that balances pro- and anti-inflammatory responses. However, modulation of splenic immune activity is a largely unexplored potential therapeutic tool that could be used for the treatment of inflammatory and life-threatening conditions. This review discusses some of the mechanisms controlling neuroimmune communication and the brain-spleen axis.

Central administration of neuropeptide Y reduces the cellular heat stress response and may enhance spleen antioxidative functions in heat-exposed chicks

Previously it was found that mRNA expression of neuropeptide Y (NPY) was increased in the chicken brain under heat stress. NPY has also been reported as an anti-stress factor to regulate brain functions in heat-exposed chicks. However, to the best of our knowledge, there is no report on the action of central NPY in the immune organs under heat stress. The aim of this study was to examine whether central injection of NPY can regulate heat stress response in the spleen and liver. After intracerebroventricular (ICV) injection of NPY, chicks were exposed to control thermoneutral temperature (CT: 30 ± 1 °C) or high ambient temperature (HT: 35 ± 1 °C) chambers for 60 min. Central injection of NPY caused lowering in rectal temperature under CT, but not under HT. Moreover, ICV injection of NPY caused a significant lower mRNA expression of heat-shock protein-70 and higher expression of glutathione synthase in the spleen, but not liver. Furthermore, plasma uric acid concentrations were significantly increased by the ICV injection of NPY in chicks under HT. These results indicate that brain NPY may contribute to attenuate the intracellular heat stress response and enhance antioxidative status in the immune organ, spleen in chicks.

Somatosensory and autonomic neuronal regulation of the immune response

Bidirectional communication between the peripheral nervous system (PNS) and the immune system is a crucial part of an effective but balanced mammalian response to invading pathogens, tissue damage and inflammatory stimuli. Here, we review how somatosensory and autonomic neurons regulate immune cellular responses at barrier tissues and in peripheral organs. Immune cells express receptors for neuronal mediators, including neuropeptides and neurotransmitters, allowing neurons to influence their function in acute and chronic inflammatory diseases. Distinct subsets of peripheral sensory, sympathetic, parasympathetic and enteric neurons are able to signal to innate and adaptive immune cells to modulate their cellular functions. In this Review, we highlight recent studies defining the molecular mechanisms by which neuroimmune signalling mediates tissue homeostasis and pathology. Understanding the neural circuitry that regulates immune responses can offer novel targets for the treatment of a wide array of diseases.

Nervous system control of intestinal host defense in C. elegans

Interplay between the nervous and immune systems is critical for homeostasis, and its dysfunction underlies pathologies such as multiple sclerosis, autism, leukemia, and inflammation. The nematode Caenorhabditis elegans provides an opportunity to define evolutionarily conserved mechanisms of regulation of host innate immunity and inflammation in a genetically tractable whole-animal system. In the past few years, the C. elegans nervous system has emerged as an integral part of host defense against pathogens, acting through diverse mechanisms to repress or induce protective transcriptional responses to infection in distal tissues. In this review, we discuss current knowledge of the mechanisms through which the C. elegans nervous system controls the expression of host defense genes in the intestinal epithelium. Although still incomplete, the insights derived from such work have broad implications for neural regulation of epithelial function at mucosal barriers in higher organisms in health and disease.

Immunohistochemical analysis of the mouse celiac ganglion: An integrative relay station of the peripheral nervous system

Celiac ganglia are important sites of signal integration and transduction. Their complex neurochemical anatomy has been studied extensively in guinea pigs but not in mice. The goal of this study was to provide detailed neurochemical characterization of mouse celiac ganglia and noradrenergic nerves in two target tissues, spleen and stomach. A vast majority of mouse celiac neurons express a noradrenergic phenotype, which includes tyrosine hydroxylase (TH), vesicular monoamine transporter 2, and the norepinephrine transporter. Over 80% of these neuron also express neuropeptide Y (NPY), and this coexpression is maintained by dissociated neurons in culture. Likewise, TH and NPY were colocalized in noradrenergic nerves throughout the spleen and in stomach blood vessels. Somatostatin was not detected in principal neurons but did occur in small, TH-negative cells presumed to be interneurons and in a few varicose nerve fibers. Cholinergic nerves provided the most abundant input to the ganglia, and small percentages of these also contained nitric oxide synthase or vasoactive intestinal polypeptide. A low-to-moderate density of nerves also stained separately for the latter markers. Additionally, nerve bundles and varicose nerve fibers containing the sensory neuropeptides, calcitonin gene-related polypeptide, and substance P, occurred at variable density throughout the ganglia. Collectively, these findings demonstrate that principal neurons of mouse celiac ganglia have less neurochemical diversity than reported for guinea pig and other species but receive input from nerves expressing an array of neurochemical markers. This profile suggests celiac neurons integrate input from many sources to influence target tissues by releasing primarily norepinephrine and NPY.

Toward the Existence of a Sympathetic Neuroplasticity Adaptive Mechanism Influencing the Immune Response. A Hypothetical View-Part I

The nervous system exerts a profound influence on the function of the immune system (IS), mainly through the sympathetic arm of the autonomic nervous system. In fact, the sympathetic nervous system richly innervates secondary lymphoid organs (SLOs) such as the spleen and lymph nodes. For decades, different research groups working in the field have consistently reported changes in the sympathetic innervation of the SLOs during the activation of the IS, which are characterized by a decreased noradrenergic activity and retraction of these fibers. Most of these groups interpreted these changes as a pathological phenomenon, referred to as "damage" or "injury" of the noradrenergic fibers. Some of them postulated that this "injury" was probably due to toxic effects of released endogenous mediators. Others, working on animal models of chronic stimulation of the IS, linked it to the very chronic nature of processes. Unlike these views, this first part of the present work reviews evidence which supports the hypothesis of a specific adaptive mechanism of neural plasticity from sympathetic fibers innervating SLOs, encompassing structural and functional changes of noradrenergic nerves. This plasticity mechanism would involve segmental retraction and degeneration of these fibers during the activation of the IS with subsequent regeneration once the steady state is recovered. The candidate molecules likely to mediate this phenomenon are also here introduced. The second part will extend this view as to the potential changes in sympathetic innervation likely to occur in inflamed non-lymphoid peripheral tissues and its possible immunological implications.

Neuro-Immune Cell Units: A New Paradigm in Physiology

The interplay between the immune and nervous systems has been acknowledged in the past, but only more recent studies have started to unravel the cellular and molecular players of such interactions. Mounting evidence indicates that environmental signals are sensed by discrete neuro-immune cell units (NICUs), which represent defined anatomical locations in which immune and neuronal cells colocalize and functionally interact to steer tissue physiology and protection. These units have now been described in multiple tissues throughout the body, including lymphoid organs, adipose tissue, and mucosal barriers. As such, NICUs are emerging as important orchestrators of multiple physiological processes, including hematopoiesis, organogenesis, inflammation, tissue repair, and thermogenesis. In this review we focus on the impact of NICUs in tissue physiology and how this fast-evolving field is driving a paradigm shift in our understanding of immunoregulation and organismal physiology.

Identification and characterization of a novel neuropeptide (neuropeptide Y-HS) from leech salivary gland of Haemadipsa sylvestris

The present study was designed to identify immunomodulatory components from the leech salivary gland of Haemadipsa sylvestris. The Sephadex G-50, Resource(TM) S column chromatography and reverse-phase high performance liquid chromatography (RP-HPLC) were used to isolate and purify the salivary gland extracts (SGE). Structural analysis of isolated compounds was based on Edman degradation and matrix assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOF-MS). The cDNA encoding the precursor of the compound was cloned from the cDNA library of the salivary gland of H. sylvestris. The levels of inflammatory mediators, including tumor necrosis factor-α (TNF-α), interferon γ (IFN-γ), interleukin-6 (IL-6), and monocyte chemotactic protein-1 (MCP-1) were assayed using an enzyme-linked immunosorbent assay (ELISA). The effects on cell proliferation and cell viability were observed using MTT assay. A novel neuropeptide Y (Neuropeptide Y-HS) from the leech salivary gland of H. sylvestris was purified and characterized. It was composed of 36 amino acid residues and the amino acid sequence was determined to be FLEPPERPAVFTSVEQMKSYIKALNDYYLLLGRPRF-NH2, containing an amidated C-terminus. It showed significant inhibitory effects on the production of inflammatory cytokines including TNF-α, IFN-γ, IL-6, and MCP-1. Neuropeptide Y was identified from leeches for the first time. The presence of neuropeptide Y-HS in leech salivary gland may help get blood meal from hosts and inhibit inflammation.

The role of the neuropeptide Y (NPY) family in the pathophysiology of inflammatory bowel disease (IBD)

Inflammatory bowel disease (IBD) includes three main disorders: ulcerative colitis, Crohn's disease, and microscopic colitis. The etiology of IBD is unknown and the current treatments are not completely satisfactory. Interactions between the gut neurohormones and the immune system are thought to play a pivot role in inflammation, especially in IBD. These neurohormones are believed to include members of the neuropeptide YY (NPY) family, which comprises NPY, peptide YY (PYY), and pancreatic polypeptide (PP). Understanding the role of these peptides may shed light on the pathophysiology of IBD and potentially yield an effective treatment tool. Intestinal NPY, PYY, and PP are abnormal in both patients with IBD and animal models of human IBD. The abnormality in NPY appears to be primarily caused by an interaction between immune cells and the NPY neurons in the enteric nervous system; the abnormalities in PYY and PP appear to be secondary to the changes caused by the abnormalities in other gut neurohormonal peptides/amines that occur during inflammation. NPY is the member of the NPY family that can be targeted in order to decrease the inflammation present in IBD.

The homeostatic role of neuropeptide Y in immune function and its impact on mood and behaviour

Neuropeptide Y (NPY), one of the most abundant peptides in the nervous system, exerts its effects via five receptor types, termed Y1, Y2, Y4, Y5 and Y6. NPY's pleiotropic functions comprise the regulation of brain activity, mood, stress coping, ingestion, digestion, metabolism, vascular and immune function. Nerve-derived NPY directly affects immune cells while NPY also acts as a paracrine and autocrine immune mediator, because immune cells themselves are capable of producing and releasing NPY. NPY is able to induce immune activation or suppression, depending on a myriad of factors such as the Y receptors activated and cell types involved. There is an intricate relationship between psychological stress, mood disorders and the immune system. While stress represents a risk factor for the development of mood disorders, it exhibits diverse actions on the immune system as well. Conversely, inflammation is regarded as an internal stressor and is increasingly recognized to contribute to the pathogenesis of mood and metabolic disorders. Intriguingly, the cerebral NPY system has been found to protect against distinct disturbances in response to immune challenge, attenuating the sickness response and preventing the development of depression. Thus, NPY plays an important homeostatic role in balancing disturbances of physiological systems caused by peripheral immune challenge. This implication is particularly evident in the brain in which NPY counteracts the negative impact of immune challenge on mood, emotional processing and stress resilience. NPY thus acts as a unique signalling molecule in the interaction of the immune system with the brain in health and disease.

Stress induced neuroendocrine-immune plasticity: A role for the spleen in peripheral inflammatory disease and inflammaging?

Research over the past decade has revealed close interaction between the nervous and immune systems in regulation of peripheral inflammation linking psychosocial stress with chronic somatic disease and aging. Moreover emerging data suggests that chronic inflammations lead to a pro-inflammatory status underlying premature aging called inflammaging. In this context, the spleen can be seen as a switch board monitoring peripherally derived neuroendocrine-immune mediators in the blood and keeping up a close communication with the central stress response via its mainly sympathetic innervation. The effect aims at balanced and well-timed stress axis activation and immune adaptation in acute peripheral inflammatory events. Constant adjustment to the needs generated by environmental and endogenous challenges is provided by neuroendocrine-immune plasticity. However, maladaptive plasticity induced e.g., by chronic stress-axis activation and excessive non-neuronal derived neuroendocrine mediators may be at the heart of the observed stress sensitivity promote inflammaging under chronic inflammatory conditions. We here review the role of neurotransmitters, neuropeptides and neurotrophins as stress mediators modulating the immune response in the spleen and their potential role in inflammaging.

NPY and NPY receptors in airway structural and inflammatory cells in allergic asthma

PURPOSE

Neuropeptide Y (NPY) level is elevated in allergic asthmatic airways and activation of NPY receptor-1 (NPY-Y1) on antigen-presenting cells (APCs) is essential for T cell priming. Paradoxically, NPY-Y1 modulates hyper-responsiveness in T cells, suggesting a bimodal role for NPY in APCs and T cells. Therefore, determination of the temporal and spatial expression pattern of NPY and its receptors in asthmatic airways is essential to further understand the role of NPY in allergic asthma.

METHODS

Lungs were isolated from control and acute and chronic stages of OVA-sensitized and challenged mice (OVA). Stains, including H&E, PAS, and trichrome, were used to determine the severity of lung pathology. The expression patterns of NPY and NPY-Y receptors in the airways were determined using ELISA and immunofluorescence. Cytokine levels in the BALF were also measured.

RESULTS

NPY levels were undetectable in the BALF of control mice, but significantly increased in the OVA group at day 80. Levels of IL-4, TGF-β1 and TGF-β2, significantly increased and peaked on day 45 and decreased on day 80 in the OVA group, exhibiting an inverse correlation with NPY levels. NPY expression was localized to macrophage-like cells in the peri-bronchial and peri-vascular areas in the lung tissue. NPY-Y1 and -Y5 receptors were constitutively expressed by both structural and inflammatory cells in the lung tissue.

CONCLUSIONS

NPY produced by activated macrophage-like cells may be involved in regulating cytokine production and cellular activities of immune cells in asthma. However, it remains unclear whether such an increase in NPY is a defensive/compensatory mechanism to modulate the effects of inflammatory cytokines.

NPY and stress 30 years later: the peripheral view

Almost 30 years ago, neuropeptide Y (NPY) was discovered as a sympathetic co-transmitter and one of the most evolutionarily conserved peptides abundantly present all over the body. Soon afterward, NPY's multiple receptors were characterized and cloned, and the peptide's role in stress was first documented. NPY has proven to be pivotal for maintaining many stress responses. Most notably, NPY is known for activating long-lasting vasoconstriction in many vascular beds, including coronary arteries. More recently, NPY was found to play a role in stress-induced accretion of adipose tissue which many times can lead to detrimental metabolic changes. It is however due to its prominent actions in the brain, one of which is its powerful ability to stimulate appetite as well as its anxiolytic activities that NPY became a peptide of importance in neuroscience. In contrast, its actions in the rest of the body, including its role as a stress mediator, remained, surprisingly underappreciated and not well understood. Our research has focused on that other, "peripheral" side of NPY. In this review, we will discuss those actions of NPY on the cardiovascular system and metabolism, as they relate to adaptation to stress, and attempt to both distinguish NPY's effects from and integrate them with the effects of the classical stress mediators, glucocorticoids, and catecholamines. To limit the bias of someone (ZZ) who has viewed the world of stress through the eyes of NPY for over 20 years, fresh insight (DH) has been solicited to more objectively assess NPY's contributions to stress-related diseases and the body's ability to adapt to stress.

Neuroimmunological response of beluga whales (Delphinapterus leucas) to translocation and a novel social environment

This study assessed changes in phagocyte function and activation of the sympatho-adrenal medullary and hypothalamo-pituitary adrenal axes of beluga whales (Delphinapterus leucas) in response to translocation and introduction to a novel social environment. Transported belugas exhibited increases in epinephrine (E), norepinephrine (NE), and cortisol levels in response to the translocation process. In response to the introduction of the transported belugas, resident belugas exhibited an increase in E and NE but not cortisol. Moreover, the increase in E and NE shown by the transported belugas was significantly greater than the increase exhibited by the resident belugas. Resident belugas exhibited a concomitant decrease in neutrophil and monocyte phagocytosis associated with the introduction of the transported belugas. In contrast, transported belugas exhibited an attendant increase in phagocytosis and respiratory burst activity immediately following transport. Differences in phagocyte response may derive from differences in hormonal milieu, stressor modality and/or intensity, or phagocyte priming. Investigating the complex interactions between types of stressors, neuroendocrine response, and immunocompetence will lead to a better understanding of the impacts of environmental challenges, including anthropogenic perturbations, on the health of cetacean populations.

Role of neuropeptide Y in the immune system and the pathogenesis of ulcerative colitis

The pathogenesis of ulcerative colitis (UC) remains unclear. Immune dysfunction has been considered to be main etiological factor for UC. Increasing evidence suggests that neuropeptide Y (NPY) is involved in immune dysfunction and the pathogenesis of UC. This paper reviews the latest advances in understanding the role of NPY in the immune system and the pathogenesis of UC.

Generating diversity: Mechanisms regulating the differentiation of autonomic neuron phenotypes

Sympathetic and parasympathetic postganglionic neurons innervate a wide range of target tissues. The subpopulation of neurons innervating each target tissue can express unique combinations of neurotransmitters, neuropeptides, ion channels and receptors, which together comprise the chemical phenotype of the neurons. The target-specific chemical phenotype shown by autonomic postganglionic neurons arises during development. In this review, we examine the different mechanisms that generate such a diversity of neuronal phenotypes from the pool of apparently homogenous neural crest progenitor cells that form the sympathetic ganglia. There is evidence that the final chemical phenotype of autonomic postganglionic neurons is generated by both signals at the level of the cell body that trigger cell-autonomous programs, as well as signals from the target tissues they innervate.

Splenic nerve is required for cholinergic antiinflammatory pathway control of TNF in endotoxemia

The autonomic nervous system maintains homeostasis through its sympathetic and parasympathetic divisions. During infection, cells of the immune system release cytokines and other mediators that cause fever, hypotension, and tissue injury. Although the effect of cytokines on the nervous system has been known for decades, only recently has it become evident that the autonomic nervous system, in turn, regulates cytokine production through neural pathways. We have previously shown that efferent vagus nerve signals regulate cytokine production through the nicotinic acetylcholine receptor subunit alpha7, a mechanism termed "the cholinergic antiinflammatory pathway." Here, we show that vagus nerve stimulation during endotoxemia specifically attenuates TNF production by spleen macrophages in the red pulp and the marginal zone. Administration of nicotine, a pharmacological agonist of alpha7, attenuated TNF immunoreactivity in these specific macrophage subpopulations. Synaptophysin-positive nerve endings were observed in close apposition to red pulp macrophages, but they do not express choline acetyltransferase or vesicular acetylcholine transporter. Surgical ablation of the splenic nerve and catecholamine depletion by reserpine indicate that these nerves are catecholaminergic and are required for functional inhibition of TNF production by vagus nerve stimulation. Thus, the cholinergic antiinflammatory pathway regulates TNF production in discrete macrophage populations via two serially connected neurons: one preganglionic, originating in the dorsal motor nucleus of the vagus nerve, and the second postganglionic, originating in the celiac-superior mesenteric plexus, and projecting in the splenic nerve.

On the mechanisms and putative pathways involving neuroimmune interactions

Bidirectional interdependence between the immune system and the CNS involves the intervention of common cofactors. Cytokines are endogenous to the brain, endocrine and immune systems. These shared ligands are used as a chemical language for communication. Such interaction suggests an immunoregulatory role for the brain, and a sensory function for the immune system. Interplay between the immune, nervous and endocrine systems is associated with effects of stress on immunity. Cytokines are thus capable of modulating responses in the CNS, while neuropeptides can exert their effects over cellular groups in the immune system. One way is controlled by the HPA axis, a coordinator of neuroimmune interactions that is essential to unravel in order to elucidate vital communications in a manner that this crosstalk remains a cornerstone in perpetuating a stance of homeostasis.

Sympathetic modulation of immunity: relevance to disease

Optimal host defense against pathogens requires cross-talk between the nervous and immune systems. This paper reviews sympathetic-immune interaction, one major communication pathway, and its importance for health and disease. Sympathetic innervation of primary and secondary immune organs is described, as well as evidence for neurotransmission with cells of the immune system as targets. Most research thus far has focused on neural-immune modulation in secondary lymphoid organs, has revealed complex sympathetic modulation resulting in both potentiation and inhibition of immune functions. SNS-immune interaction may enhance immune readiness during disease- or injury-induced 'fight' responses. Research also indicate that dysregulation of the SNS can significantly affect the progression of immune-mediated diseases. However, a better understanding of neural-immune interactions is needed to develop strategies for treatment of immune-mediated diseases that are designed to return homeostasis and restore normal functioning neural-immune networks.

The Y1 receptor for NPY: a key modulator of the adaptive immune system

Growing evidence suggests that the neuropeptide Y (NPY) system plays an important role in the immune system. Yet, little is known about the expression of NPY and receptors in the immune system. Moreover, original contradicting results have confused the picture and hampered a clear understanding of its role in the immune system. The use of Y(1) receptor-deficient mice, combined with advanced methods to investigate immune functions, have provided the solution to the problem raised by previous disparities. From results obtained using Y(1)-deficient mice (Y(1)(-/-)), we uncovered a bimodal role for Y(1) on immune cells. Y(1) expression on antigen-presenting cells (APC) is essential for their function as T cell priming elements. Conversely, Y(1) signaling in T cells plays a regulatory role without which T cells are hyper-responsive. The opposite role of Y(1) on APC and T cells has reconciled previous disparities by showing that signaling via Y(1) protects against inflammation by inhibiting T cell responses, whereas Y(1)(-/-) mice are protected in the same inflammatory models due to defective APCs.

Neuropeptide Y Y1 receptors mediate morphine-induced reductions of natural killer cell activity

Morphine suppresses a number of immune parameters, such as natural killer (NK) cell activity and lymphocyte proliferation, by acting through mu-opioid receptors in the central nervous system. Prior studies have implicated the sympathetic nervous system in mediating the immunomodulatory effects of acute morphine treatment. However, the peripheral mechanism whereby morphine inhibits NK cell activity is not fully understood. The aim of the present study was to investigate the role of the sympathetic transmitter neuropeptide Y (NPY) in mediating morphine-induced immune alterations. The results showed that administration of the selective NPY Y1 receptor antagonist BIBP3226 blocked morphine's effect on splenic NK activity but did not attenuate the suppression splenocyte proliferative responses to Con-A or LPS. Furthermore, intravenous NPY administration produced a dose-dependent inhibition of splenic NK activity but did not suppress lymphocyte proliferation. Recent studies from our laboratory have demonstrated that morphine modulates NK activity through a central mechanism that requires the activation of dopamine D1 receptors in the nucleus accumbens. Results from the present study showed that microinjection of the D1 receptor agonist SKF-38393 into the nucleus accumbens shell induced a suppression of NK activity that was reversed by BIBP3226. Collectively, these findings demonstrate that NPY Y1 receptors mediate morphine's suppressive effect on NK activity and further suggest that opioid-induced increases in nucleus accumbens D1 receptor activation inhibit splenic NK activity via NPY released from the sympathetic nervous system.

Effects of moxibustion to zusanli (ST36) on alteration of natural killer cell activity in rats

Moxibustion is one of the major healing techniques in Oriental medicine. It has been widely used in many diseases such as rheumatoid arthritis, Hashimoto disease, breech presentation, etc. However, till now, effects of moxibustion on natural killer (NK) cell activity and relations between sympathetic nerve system (SNS) and the immune alteration induced by moxibustion were not well studied. This study was designed to evaluate effects of moxibustion on NK cell activity and the intervention of SNS in the alteration of NK cell activity induced by moxibustion. Splenic NK cell cytotoxicity was measured in a standard 4-hour 51Cr release assay. We measured the NK cell cytotoxicity after moxibustion stimulation for 1, 3, 5 and 7 days, and also measured the NK cell cytotoxicity after 3 and 7 days burn stimulation with similar temperature. Interleukin (IL)-2, -4 and interferon (INF)-gamma in serum were measured by rat IL-2, -4 and INF-gamma ELISA test kit. To evaluate the effects of sympathectomy on alteration of NK cell cytotoxicity, 6-hydroxydopamine (6-OHDA: 50 mg/kg) was used. We showed that NK cell activity of moxibustion stimulation group increased at the 3rd day, and declined at the 7th day in comparison with that of the control group. In the moxibustion stimulation group, NK cell activity was significantly higher than the sham group at the 3rd day. On the contrary, in the burn stimulation group, NK cell activity was significantly higher than that of the sham groups at 3rd and 7th days. INF-gamma level after 3 days in the moxibustion stimulation group was significantly higher than that of the sham group. IL-2 level among groups were not different. IL-4 was not detected in serum with this method. Sympathectomy abolished the NK cell activity alteration induced by moxibustion. The results suggest that moxibustion modulates NK cell activity, along with INF-gamma, and SNS is mediating these effects.

Autonomic innervation of immune organs and neuroimmune modulation

1. Increasing evidence indicates the occurrence of functional interconnections between immune and nervous systems, although data available on the mechanisms of this bi-directional cross-talking are frequently incomplete and not always focussed on their relevance for neuroimmune modulation. 2. Primary (bone marrow and thymus) and secondary (spleen and lymph nodes) lymphoid organs are supplied with an autonomic (mainly sympathetic) efferent innervation and with an afferent sensory innervation. Anatomical studies have revealed origin, pattern of distribution and targets of nerve fibre populations supplying lymphoid organs. 3. Classic (catecholamines and acetylcholine) and peptide transmitters of neural and non-neural origin are released in the lymphoid microenvironment and contribute to neuroimmune modulation. Neuropeptide Y, substance P, calcitonin gene-related peptide, and vasoactive intestinal peptide represent the neuropeptides most involved in neuroimmune modulation. 4. Immune cells and immune organs express specific receptors for (neuro)transmitters. These receptors have been shown to respond in vivo and/or in vitro to the neural substances and their manipulation can alter immune responses. Changes in immune function can also influence the distribution of nerves and the expression of neural receptors in lymphoid organs. 5. Data on different populations of nerve fibres supplying immune organs and their role in providing a link between nervous and immune systems are reviewed. Anatomical connections between nervous and immune systems represent the structural support of the complex network of immune responses. A detailed knowledge of interactions between nervous and immune systems may represent an important basis for the development of strategies for treating pathologies in which altered neuroimmune cross-talking may be involved.

Effect of calcitonin gene-related peptide, neuropeptide Y, substance P, and vasoactive intestinal peptide on interleukin-1beta, interleukin-6 and tumor necrosis factor-alpha production by peripheral whole blood cells from rheumatoid arthritis and osteoarthritis patients

In the present study, we have investigated the in vitro effect of calcitonin-related peptide (CGRP), neuropeptide Y (NPY), substance P (SP) and vasoactive intestinal peptide (VIP) at concentrations of 10(-8), 10(-9) and 10(-10) M on the production of different proinflammatory cytokines or chemokines such as IL-1beta, IL-6 and TNFalpha by peripheral whole blood cells from patients with rheumatoid arthritis, as well as from osteoarthritis patients studied as a control group without immunoinflammatory background. We have found that CGRP, NPY, SP and VIP stimulated significantly the production of those cytokines and chemokines in rheumatoid arthritis patients. In general, the stimulation was higher at the 10(-9) M concentration, with SP and VIP, and in rheumatoid arthritis patients compared to osteoarthritis ones. Neuropeptides did not significantly modify the LPS-induced cytokine production by whole blood cells. The results indicate that physiological concentrations of the neuropeptides studied can modulate the inflammatory and immunological response, stimulating significantly the production of inflammatory cytokines by human whole blood cells in rheumatoid arthritis patients, as well as, in a minor way, in osteoarthritis patients.

Neuropeptide Y effects on murine natural killer activity: changes with ageing and cAMP involvement

Changes in the bidirectional interaction between the nervous and the immune systems have been proposed as a cause of ageing. Neuropeptides, such as neuropeptide Y (NPY), could show different effects on immune function with age. In the present work, we have studied the in vitro action of a wide range of NPY concentrations, i.e. from 10(-13) to 10(-7) M, on natural killer (NK) activity, a function which decreases with age. Spleen, axillary nodes, thymus and peritoneum leukocytes from mice of different ages: young (12+/-2 weeks), adult (24+/-2 weeks), mature (50+/-2 weeks) and old (72+/-2 weeks) were used. Stimulation by NPY of NK activity was observed in adult and mature animals in axillary nodes and thymus, and an inhibition in the spleen from young mice. The specificity of the NPY effect on cytotoxic activity was confirmed using a C-terminal fragment of NPY. Furthermore, cAMP levels in leukocytes were found to be decreased by NPY in adult mice, suggesting an involvement of this messenger system in the NK modulation by this neuropeptide.

Effects of interleukin-2 on the expression of corticotropin-releasing hormone in nerves and lymphoid cells in secondary lymphoid organs from the Fischer 344 rat

This study examined the influence of interleukin (IL)-2 on corticotropin releasing hormone (CRH) immunoreactivity in the Fischer 344 (F344) rat spleen. Rats were given either vehicle or 1, 10, 25, 50, 100, or 200 ng of human recombinant (hr)IL-2 by intraperitoneal (i.p.) injection, and were sacrificed 0.5, 1, 4, 12, or 24 h after treatment. Spleens and mesenteric lymph nodes were prepared for immunocytochemistry to localize CRH. In spleens from vehicle-treated animals, CRH immunoreactivity was present in several types of cells of the immune system, but CRH(+) nerves were not observed in either spleens or lymph nodes from vehicle-treated animals. Treatment with IL-2 induced CRH expression in nerves in the spleen in a dose- and time-dependent manner. CRH(+) nerves were not found in the mesenteric lymph nodes after IL-2 treatment, instead a dramatic time- and dose-dependent accumulation of CRH(+) cells (resembling small lymphocytes and large granular mononuclear cells) in the cortex and medulla. These findings indicate that IL-2 stimulates the synthesis of CRH in nerves that innervate the F344 rat spleen, and promote the appearance of CRH(+) immunocytes into draining mesenteric lymph nodes.

Changes with aging in the modulation by neuropeptide Y of murine peritoneal macrophage functions

Some age-related changes in immune function may be due, at least in part, to a disturbance in the communication between the nervous and immune systems. In the present work, the effects in vitro of neuropeptide Y (NPY) (10(-13) to 10(-7) M) on different peritoneal macrophage functions (adherence to substrate, chemotaxis, phagocytosis, superoxide anion production, and the release of TNFalpha and IL-1beta) have been studied on cells from young (12+/-2 weeks), adult (24+/-2 weeks), mature (50+/-2 weeks) and old (72+/-2 weeks) BALB/c mice. The specificity of these actions was confirmed using two C-terminal fragments of NPY, and the intracellular messengers (protein kinase C and cAMP) involved in the action of the neuropeptide were also analyzed. The results show that the functions studied change with aging and that the effects of NPY on each function, which are carried out through specific receptors, as well as on intracellular pathway, differ depending on age, maintaining the immune functions at physiologically adequate levels in old animals.

The NPY effects on murine leukocyte adherence and chemotaxis change with age. Adherent cell implication

The two-way communication between the nervous and immune system is currently well-known, but the age-related changes in this communication have been scarcely studied. In the present work, we have investigated the in vitro effects of neuropeptide Y (NPY) at concentrations ranging from 10(-13) to 10(-7) M on the adherence and chemotaxis capacities of spleen, axillary node, thymus and peritoneum leukocytes from BALB/c mice. The NPY effect on these functions was examined on cells from animals of four different ages, i.e. young (12+/-2 weeks old), adult (24+/-2 weeks old), mature (50+/-2 weeks old) and old (72+/-2 weeks old). In young animals, NPY stimulates the adherence of leukocytes from spleen, axillary nodes and thymus and inhibits it in cells from peritoneum. In adult animals NPY inhibits the adherence of leukocytes from thymus. These effects disappear with ageing in all locations. Chemotaxis is stimulated by this neuropeptide at all ages in cells from axillary nodes and peritoneum, but this effect is absent in old mice. NPY exerts an inhibitory effect on the chemotaxis of leukocytes from thymus at all ages studied. These NPY effects on leukocytes seem to be carried out through adherent cells.

Activity-wheel running blunts suppression of splenic natural killer cell cytotoxicity after sympathectomy and footshock

We used chemical sympathectomy by 6-hydroxydopamine (6-OHDA) to examine whether adaptation by the sympathetic nervous system (SNS) is a plausible explanation for our prior finding that activity-wheel running blunts the suppression of splenic natural killer cell cytotoxicity after footshock. Male Fischer rats were assigned to treatments using a group (activity wheel vs. sedentary)x treatment (6-OHDA vs. saline)x condition (footshock vs. no shock) design. After 5-6 weeks, rats were injected i.p. with saline or with 40, 80, and 80 mg/kg 6-OHDA on pre experimental days -5, -3, and -1. Half the rats received 6 min of random footshock during a 40-min period. Cytotoxicity was determined by standard 4-h 51Cr release assay. Sympathectomy reduced splenic [NE] by 72%. After 6-OHDA injection and footshock, percent lysis was 33% lower in sedentary rats compared with activity-wheel runners and home-cage controls, p=0.048. The results suggest that activity-wheel running leads to adaptations that offset an altered SNS modulation of splenic NK cell cytotoxicity in response to footshock.

Age-related changes in the neuropeptide Y effects on murine lymphoproliferation and interleukin-2 production

Neuropeptide Y (NPY) modulates several aspects of the immune response but it is not known whether NPY responsiveness is altered with aging. In this work, the in vitro effect of NPY at concentrations ranging from 10(-)(14) M to 10(-)(7) M on lymphoproliferation has been studied in spleen, axillary node and thymus leukocytes from young, adult, mature and old BALB/c mice. The spontaneous proliferation of spleen lymphocytes from young mice was significantly stimulated by NPY. In response to the mitogen Con A, lymphoproliferation and IL-2 release by lymphocytes were inhibited significantly by NPY, these effects disappearing with aging. The results show that NPY is a modulator of lymphoproliferation and that this effect disappears progressively with age. Moreover, this regulatory role of NPY may be carried out through a decrease in IL-2 production.

Changes with ageing in the modulation of murine lymphocyte chemotaxis by CCK-8S, GRP and NPY

The general immunodepression found in ageing organisms may be related to changes in the neuroimmune network. In the present study, the migration capacity of lymphocytes from BALB/c mice of three different ages: young (12 +/- 2 weeks), adult (24 +/- 2 weeks) and old (72 +/- 2 weeks), has been assayed in vitro in response to three neuropeptides: sulfated cholecystokinin octapeptide (CCK-8s), gastrin-releasing peptide (GRP) and neuropeptide Y (NPY) in a physiological range of concentrations (10(-8)-10(-12) M). The capacity of migration to a chemical gradient or chemotaxis was studied by the Boyden's technique using f-met-leu-phe at 10(-8) M as chemoattractant. The results show a different response of lymphocytes to the different neuropeptides, as wells as to age, concentrations and locations studied. However, some similarities were found, for instance the three neuropeptides inhibited chemotaxis in thymus. The stimulatory effects that GRP and NPY exerted in young and adult mice were not observed in old animals. CCK-8s inhibited the chemotaxis in every organ studied, with the effect being more striking in old mice. Our conclusion is that stimulatory effects of the neuropeptides disappear or become inhibitory with ageing.

Alterations in sympathetic noradrenergic innervation in lymphoid organs with age

Previous work in our laboratories has shown a selective age-related loss of sympathetic noradrenergic (NA) nerves from the spleen and lymph nodes of rats. In contrast, NA nerve fiber density is dramatically increased in the thymus of aged mice and rats. We hypothesize that the diminished splenic NA innervation in old rats is due to cumulative oxidative metabolic autodestruction of NA nerve terminals by high concentrations of norepinephrine released during specific time periods of immunologic reactivity. These old animals show a loss of NK cell activity, diminished T-cell proliferation, and diminished cell-mediated immunity. To assess the plasticity of NA nerve fibers in the aged rat spleen, male Fischer 344 rats at 24 months of age were treated for 2 months with daily injections of 0.25 or 1.0 mg/kg/day of L-deprenyl, followed by a 10-day drug washout period. The L-deprenyl-treated rats showed a remarkable sprouting of NA nerves into the splenic white pulp, with regrowth into appropriate vascular and parenchymal compartments. Rats with enhanced NA nerve regrowth showed increased IL-2 and IFN-gamma production and NK cell activity compared with vehicle injected or uninjected age-matched control rats. We proposed that L-deprenyl stimulates NA nerve regrowth into secondary lymphoid organs, which leads to partial recovery of measures of immunosenescence.

Comparison between the effects of sigma receptor ligand JO 1784 and neuropeptide Y on immune functions

Recent evidence suggests that sigma receptor ligands and neuropeptide Y may act through the same pathways to modulate centrally mediated immune function. The present study demonstrated that both the sigma receptor ligand igmesine: (+)-N-cyclopropylmethy-N-methyl-1, 4-diphenyl-1-yl-but-3-en-1-ylamine, hydrochloride (JO 1784) (10(-7) and 10(-5) M) and neuropeptide Y (10(-9) and 10(-7) M) in vitro significantly reduced neutrophil phagocytosis and decreased mitogen stimulated lymphocyte proliferation. By contrast, central administration of JO 1784 (0.5 and 5 microg/5 microl) significantly reduced the activity of neutrophil phagocytosis, but enhanced lymphocyte proliferation without changing the serum concentration of corticosterone. Neuropeptide Y (10(-9) and 10(-7) M), following intracerebroventricular infusion, also decreased the neutrophil response, but significantly raised the corticosterone concentration. These results indicate that different mechanisms (involving various neurotransmitters and their receptors, changes in the activity of the hypothalamic-pituitary-adrenal axis, or sigma receptor subtypes) may be involved in the central effects of JO 1784 and neuropeptide Y.

Modulation of immune cell function by the autonomic nervous system

This review discusses some of the major findings implicating the autonomic nervous system in the regulation of immune function. The sympathetic nervous system, the primary focus of this line of research, directly innervates the major lymphoid organs, and physiological release of sympathetic neurohormones at these sites has been documented. Leukocytes have been shown to express receptors for catecholamines, as well as neuropeptide Y, and studies in vitro and in vivo have indicated that occupation of these receptors by the appropriate ligands produces functional changes in immunological cells. Finally, altered sympathetic regulation may underlie some of the immunological abnormalities observed in chronic stress, clinical depression, and ageing.

Enhanced immunohistochemical detection of autonomic nerve fibers, cytokines and inducible nitric oxide synthase by light and fluorescent microscopy in rat spleen

We have developed enhanced immunohistochemical protocols for detecting autonomic nerve fibers and splenocyte-associated proteins in rat spleen. This includes norepinephrine-synthesizing enzymes (dopamine-beta hydroxylase (DBH) and tyrosine hydroxylase (TH)), neuropeptide Y (NPY), tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), c-fos protein, inducible nitric oxide synthase (iNOS), and the macrophage cell marker ED1. Animals were divided into sham-operated and splenic nerve-sectioned groups for detection of DBH, TH, and NPY. For immunodetection of TNF-alpha, iNOS, IFN-gamma and c-fos, animals were injected IV with saline or 100 microg of lipopolysaccharide (LPS) and were sacrificed at various time intervals post injection. Rats were perfused with 4% paraformaldehyde, spleens removed and cryoprotected, and 50-microm floating sections were cut on a freezing microtome. Immunodetection was performed with various detection systems and substrate/chromogen solutions, and in some cases using pretreatment with proteinase K (PK) for antigen unmasking. PK pretreatment increased immunostaining for DBH, TH, NPY, IFN-gamma, iNOS, and ED1, and the improvement was concentration-dependent. Using NPY immunostaining to index the signal-to-noise ratio for various substrates and detection systems, we found that an alkaline phosphatase detection system with NBT/BCIP as a substrate was the best procedure for light microscopy, whereas the CY3-labeled secondary antibody technique proved optimal for fluorescent microscopy. Surgical transection of the splenic nerve eliminated all nerve fiber staining for DBH, TH, and NPY. TNF-alpha, IFN-gamma, c-fos, and iNOS proteins were observed in the spleen in a time-dependent manner after LPS stimulation. Fluorescent double labeling, visualized with fluorescent confocal scanning laser microscopy, revealed many NPY fibers distributed among the ED1-labeled macrophages. These results demonstrate that immunohistochemistry can be used to index the activational effects of an immune challenge on splenocytes in situ and verifies that splenic immune cells are innervated by the sympathetic nervous system.

Effect of local autonomic denervation on in vitro responsiveness of lymphocytes from rat submaxillary lymph nodes

The local autonomic denervation of rat submaxillary lymph nodes was achieved by a unilateral sympathetic superior cervical ganglionectomy and/or the unilateral section of chorda tympani (that resulted in ipsilateral parasympathetic decentralization of the submandibular territory). This study was performed to determine: (1) whether local sympathetic and/or parasympathetic denervation of rat submaxillary lymph nodes brought about changes in lymph node cellularity, natural killer activity and lipopolysaaccharide (LPS)- and concanavalin A (Con A)-induced cell proliferation in Freund's adjuvant-injected rats; (2) whether the effect of the immunosuppressive drug cyclosporine in rat submaxillary lymph nodes was affected by a single or combined unilateral ganglionectomy plus decentralization. A unilateral ganglionectomy, or the combination of ganglionectomy plus decentralization, performed 7 days earlier, decreased significantly cellularity in ipsilateral submaxillary lymph nodes, while a unilateral decentralization failed to affect it. Natural killer activity increased ipsilaterally after ganglionectomy or decentralization, and decreased after the combined surgical procedure. LPS-induced cell proliferation augmented significantly after ganglionectomy or decentralization, while Con A-induced T lymphocyte proliferation remained unaffected. In the sham-operated side, cyclosporine decreased submaxillary lymph node cell number and natural killer activity, while it increased the proliferative response to LPS. The depressive effect of cyclosporine on lymph node cellularity was no longer observed in ganglionectomized or decentralized lymph nodes, but was found after the combined surgical denervation. Decentralization, or decentralization plus ganglionectomy, blunted the depressive effect of cyclosporine on natural killer activity. The stimulatory effect of cyclosporine on lymphocyte proliferation induced by LPS was reversed both by ganglionectomy or by decentralization and was suppressed by the combined surgical procedure. Neither treatment affected Con A-induced proliferation of T lymphocytes. The results further indicate that an appropriate sympathetic and parasympathetic local environment may be needed for immunomodulation, as well as for cyclosporine activity in lymphoid tissue.

Differential effects of gastrin-releasing peptide, neuropeptide Y, somatostatin and vasoactive intestinal peptide on interleukin-1 beta, interleukin-6 and tumor necrosis factor-alpha production by whole blood cells from healthy young and old subjects

In the present study, we have investigated the effect in vitro of gastrin-releasing peptide (GRP, 10(-10) M), neuropeptide Y (NPY, 10(-10) M), somatostatin (10(-10) M) and vasoactive intestinal peptide (VIP, 10(-9) M) on the production of IL-1 beta, IL-6 and TNF alpha by peripheral whole blood cells from healthy young and old people. We have found that GRP, NPY, somatostatin and VIP stimulated the production of IL-1 beta in old subjects, and NPY, somatostatin and VIP in young ones. In addition, the production of IL-6 was enhanced by GRP, NPY and VIP in young and old people. The TNF alpha production was stimulated by NPY and somatostatin in young subjects, and by NPY, somatostatin and VIP in old ones, whereas GRP produced a decrease of TNF alpha in young persons. GRP in old subjects and VIP in young and old subjects stimulated in a great degree the LPS-induced IL-6 production by whole blood cells. On the contrary, GRP and VIP inhibited highly the LPS-induced TNF alpha production in young controls. Our results show that these neuropeptides, when added to whole blood cells at physiological concentrations, are able to stimulate the production of IL-1 beta, IL-6 and TNF alpha in a differential way according to the subject age.

Is the pretreatment effect of low dose Freund's adjuvant on adjuvant arthritis due to an activation of the nervous system?

It has been recently shown that pretreatment with a low dose of Freund's adjuvant decreases the severity of adjuvant arthritis in rats. To study the involvement of the central and peripheral nervous systems in the pretreatment effect, concentrations of substance P (SP)-, neurokinin A (NKA)-, calcitonin gene-related peptide (CGRP)- and neuropeptide Y (NPY)-like immunoreactivities (-LI) were measured in the cerebrospinal fluid, plasma and synovial fluid 2 and 24 h after a single s.c. injection of 0.05 mg Freund's adjuvant. Increased concentrations of CGRP-LI were found in the cerebrospinal fluid, plasma and synovial fluid. NPY-LI was decreased in the cerebrospinal fluid while NKA-LI was decreased in plasma. In the synovial fluid, SP-LI was increased at 24 h and NKA-LI was increased at 2 h following treatment. Our results indicate that part of pretreatment effect of low dose of subcutaneous Freund's adjuvant in the rat may be attributed to neurogenic mechanisms.

Effects of adjuvant on neuropeptide-like immunoreactivity in experimentally induced temporomandibular arthritis in rats

Substance P (SP)-, neurokinin A (NKA)-, calcitonin gene-related peptide (CGRP)- and neuropeptide Y (NPY)-like immunoreactivities (-LI) were examined in cerebrospinal fluid (CSF), plasma and temporomandibular joint (TMJ) perfusates in rats 1 and 12 h after inoculation at the base of the tail (0.05 ml) or injection into the right TMJ (0.01 ml) of heat-killed Mycobacterium butyricum in paraffin oil. In the rats inoculated at the base of the tail (polyarthritic rats), there was a significant increase of CGRP-LI and NKA-LI. The changes in neuropeptide-LI were not as marked in the CSF of rats injected with adjuvant in one TMJ (monoarthritic rats) as in the polyarthritic group. Instead, the most significant changes in the monoarthritic rats were seen in the perfusates of both TMJs. The increases in SP-, NKA-, CGRP- and NPY-LI were significant for both TMJs and more pronounced than in the polyarthritic rats. The results show that inoculation of adjuvant at the base of the tail induces significant changes of neuropeptide-LI predominantly in CSF, whilst an intra-articular injection induces bilateral changes in neuropeptide-LI in joint perfusate. Therefore, two different neural mechanisms may be involved early in adjuvant-induced poly- and monoarthritis.

Expression of vasoactive intestinal peptide in lymphocytes: a possible endogenous role in the regulation of the immune system

Experimental evidence is accumulating showing that vasoactive intestinal peptide (VIP) acts as an immunoregulatory peptide. Findings from our laboratory and others indicate that cells of the immune system are able to produce VIP. We have detected immunoreactivity for VIP in lymphocytes by immunohistochemical methods at specific locations of both central and peripheral lymphoid organs. Double immunofluorescence staining and flow cytometry analysis indicate that both T and B lymphocytes contain VIP that has been proved to be mostly VIP 1-28 by high-performance liquid chromatography and radioimmunoassay. VIP has been also demonstrated by 'in situ' hybridization and reverse transcription followed by polymerase chain reaction. We have also detected induction of VIP in splenic lymphocytes after mitogenic stimulation. Lymphocytes should be sensitive to the endogenously produced VIP because we have also detected VIP receptor expression in different populations of lymphocytes. All this evidence indicates that VIP is an endogenous autocrine modulator of immune function.

Unexpected high density of neuropeptide Y Y1 receptors in the guinea pig spleen

Receptors for neuropeptide Y (NPY) and peptide YY (PYY) have been extensively characterized in the brain. Less is known about NPY receptor subtypes in the spleen, though it is well established that NPY produces vascular contraction in this tissue. In the present study, we found an unusually high density of Y1 receptors in the guinea pig spleen. These receptors are localized to the red pulp and exhibit a pharmacology that is consistent with the Y1 receptor. On the other hand, only very low densities for Y2 receptors were observed. Therefore, the guinea pig spleen may be a ideal tissue for further study of the role of Y1 receptors in cardiovascular and immune function.

A role for CRH and the sympathetic nervous system in stress-induced immunosuppression

Central CRH coordination of the behavioral and physiologic sequelae of stress has been well established, and so it is parsimonious to suggest that CRH might also coordinate the immunologic sequelae. The studies presented here lend support to this suggestion. CRH administration into the brain was shown to modulate aspects of both cellular and humoral immune function, and the inhibition of CRH release in the brain following stress inhibited stress-associated immunosuppression. The effects of CRH appear to be mediated by the sympathetic branch of the autonomic nervous system, as chemical sympathectomy and pharmacological blockade of beta-adrenergic receptors both reversed the effects of CRH on immune function. In contrast, removal of the adrenal glands did not alter the immunologic effects of CRH. These links among CRH in the brain, sympathetic activation, and immune function suggest the possibility that immune function may be altered in other conditions characterized by elevated sympathetic tone, such as depression and aging, and that these alterations may be attributed to CRH dysregulation in the brain. These studies shed light on the intricate relationship between the brain and the immune system, and also illuminate its complexity. The differential regulation of CRH in the brain and the periphery is one example of the latter. These findings also set the stage for potential clinical intervention with CRH antagonists, for example, to treat compromised immune function associated with chronic stress, depression, or aging.