Noradrenergic sympathetic neural interactions with the immune system: structure and function

The occurrence of neuropeptides at different stages of DBM-induced heterotopic bone formation

In developing heterotopic bone in the rat, induced by allogeneic bone matrix, we immunohistochemically detected nerves containing substance P (SP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP) and tyrosine hydroxylase (TH). After 10 days they were dicernible amidst differentiating chondroblastoid cells in fibrous tissue around and within the implants. Over the next 3 weeks, the nerves increased in number and gradually attained a shape and distribution resembling normal osseal nerves; varicose fibres frequently occurred in periosteum-like fibrous tissue and bone marrow adjacent to newly formed bone. At 8 weeks, NPY-fibres increased, particularly in the marrow and this abundance of NPY fibres remained at 16 weeks. VIP-immunoreactive fibres were only observed in the surrounding periosteum-like fibrous tissue 4-6 weeks after implantation. These observations, in combination with recent findings of receptors to neuropeptides on bone cells, suggest a neurogenic influence on physiological processes in bone tissue.

Muramyl-dipeptide, a macrophage-derived cytokine, alters neuronal activity in hypothalamus and hippocampus but not in the dorsal raphe/periaqueductal gray of rats

Muramyl-dipeptide (MDP) is derived in vivo by degradation of bacteria cell walls and is the minimum fragment that stimulates the acute phase response to bacterial infection. The present study investigates whether this specific product of an immune response affects central nervous system (CNS) function. To this end, the activity of single neurons within the hypothalamus, hippocampus, and dorsal raphe/periaqueductal gray region prior to and following systemic (i.p.) injection was studied. The results obtained from a total of 120 cells demonstrate that single hypothalamic and hippocampal neurons, sites previously shown to aid in the integration of various environmental stimuli into physiologic processes, alter their neuronal activity in site-specific manners following MDP administration. The specificity of the responses included both the threshold for activation of particular sites, effects of increasing dosages upon response pattern characteristics, and time course to the changes observed. These results therefore suggest that MDPs may play a role in the neuro-immunologic regulatory pathways during the immune response to bacterial infection.

Psychological stress and phorbol ester inhibition of radiation-induced apoptosis in human peripheral blood leukocytes

Apoptosis is a process of genetically programmed alterations of cell structure that lead to failure of proliferation and differentiation, and eventual cell death. Apoptosis is induced by a variety of toxic insults including growth factor deprivation and ionizing radiation. This process may function to protect against the appearance of heritable phenotypic changes in cells and may be a critical factor in normal cellular immune function. Phorbol esters inhibit apoptosis, but little is known about factors that regulate this process physiologically. In this study, we demonstrate an association between an acute psychological stressor, taking examinations, and the induction of substantial and reversible changes in the response of peripheral blood leukocytes to gamma irradiation and to phorbol ester treatment. These data suggest that psychological stress may induce physiological changes that regulate the ability of immune cells to initiate apoptosis.

Evidence that shock-induced immune suppression is mediated by adrenal hormones and peripheral beta-adrenergic receptors

Our previous work has demonstrated that presentations of mild foot-shock to Lewis rats induces a suppression of splenic and peripheral blood lymphocyte responses to nonspecific T-cell mitogens. The present study demonstrated that adrenalectomy prevented the shock-induced suppression of the mitogenic response of peripheral blood T-cells but did not attenuate the suppression of splenic T-cells. Conversely, the beta-adrenergic receptor antagonists, propranolol and nadolol, attenuated the shock-induced suppression of splenic T-cells in a dose-dependent manner but did not attenuate suppression of the blood mitogen response. These data indicate that distinct mechanisms mediate the shock-induced suppression of T-cell responsiveness to mitogens in the spleen and the peripheral blood. The results indicate that the peripheral release of catecholamines is responsible for splenic immune suppression and that adrenal hormones, which do not interact with beta-adrenergic receptors, are responsible for shock-induced suppression of blood mitogenic responses.

Prenatal alcohol exposure alters the development of sympathetic synaptic components and of nerve growth factor receptor expression selectivity in lymphoid organs

Exposure to alcohol in utero has been associated with long-term immune deficits. In addition, adult mice exposed to alcohol prenatally display altered noradrenergic synaptic transmission selectively in lymphoid organs. This is consistent with the hypothesis that sympathetic neurons play an important role in immunomodulation. The development and maintenance of sympathetic neurons are critically dependent on nerve growth factor (NGF). Furthermore, NGF has been shown to modulate immune responses and NGF receptor expression has been localized to lymphoid organs. The present work examined the effects of prenatal alcohol exposure on the development and maturation of pre- and postsynaptic sympathetic components, including norepinephrine and beta-adrenoceptors, respectively, as well as the early expression of NGF receptors in lymphoid and other organs of the C57BL/6 mouse. Infant mice that were exposed to alcohol in utero displayed reduced levels of norepinephrine and beta-adrenoceptor density, as well as increased NGF receptor expression in the thymus and spleen, but not the heart. These selective changes may account, in part, for the persistent immune incompetence characteristic of fetal alcohol syndrome.

Altered T-lymphocyte response following aggressive encounters in mice

Intermale aggression is a natural form of psychosocial stress that can alter a variety of physiological functions, including immune function. In Experiment 1, daily fighting between pairs of previously isolated male mice differentially altered immunological measures of T-cell responsiveness in dominant and submissive animals. Submissive mice had lower T-cell proliferation and IL-2 production, when compared to dominant, nonfought, or witness mice. Since the fighting behavior often results in wounding of the submissive animal, Experiment 2 used a relatively nonaggressive test to determine whether the immunological differences between dominant and submissive mice were due to wounding or due to the psychosocial state of dominance. Dominant mice had elevated T-cell proliferation and IL-2 production when compared to the other treatment groups. Therefore, it appears that in dominant/submissive pairs of mice a severe physical stress, such as intense fighting, influences the immune system in a different manner than psychological or mild aggressive encounters.

Immunological reactions of pigs during long-term beta-adrenergic treatment

Experiments were performed to determine the effects of the beta-adrenergic agonist Ro 16-8714 on the immune system of finishing pigs fed an adequate or a low-protein diet. Growth rate, nitrogen and fat retention, body composition as well as spleen weight were influenced by both beta-agonist and/or protein level, as expected. However, lymphocyte stimulation with Concanavalin A and phytohemagglutinine in vitro or in vivo antibody production against horse red blood cells were not changed by the beta-agonist in pigs fed sufficient or insufficient amounts of protein.

Effects of stress on the immune system

Stress, distress and a variety of psychiatric illnesses, notably the affective disorders, are increasingly reported to be associated with immunosuppression. The concept that psychic distress may predispose to medical illness is centuries old but has only recently attracted the attention of the scientific community at large. Interdisciplinary collaboration has established psychoneuroimmunology, or neuroimmunomodulation, as a new field of investigation with the goal of rigorous scientific research into the elusive mind-body connection. This has resulted in the rapid accumulation of information which falls across the boundary lines of psychiatry, immunology, neurosciences and endocrinology. Here David Khansari, Anthony Murgo and Robert Faith review the effects of stress on the endocrine and central nervous systems and the interactions between these systems and the immune response after exposure to stress signals.

Antibodies bind and activate beta adrenergic and cholinergic lymphocyte receptors in Chagas' disease

It is demonstrated that murine chagasic IgG and the corresponding F(ab')2 fragments interfere with beta adrenergic and muscarinic cholinergic specific ligand occupancy on T cell-enriched population. From the interaction between chagasic IgG or F(ab')2 with Lyt-1+ cells, an increase in cAMP levels occurs as a consequence of beta adrenergic receptor activation. On the contrary, chagasic IgG or F(ab')2 interactions with Lyt-2+ cells induce an activation of muscarinic cholinergic receptor, leading to an increment in cGMP. Muscarinic cholinergic and beta adrenergic stimulation trigger the release of PGE2 and TXB2, respectively. Lyt-2+ cells treated with chagasic IgG or F(ab')2 are able to decrease the contractility of mouse atria. The same negative inotropic effect is elicited with Lyt-2+ cells from Trypanosoma cruzi-infected mice susceptible to developed myocarditis. The implications of these results in the pathogenesis of Chagas' myocarditis are discussed.

Fluorescence histochemical techniques for catecholamines as tools in neurobiology

Formaldehyde-induced and glyoxylic-acid-induced fluorescence histochemistry permits the tissue localization of catecholamines in the central nervous system (CNS) and peripheral nervous system (PNS), and in culture. Counterstains such as ethidium bromide provide excellent background identification of specific innervated regions in both the CNS and the periphery. Use of fluorescence histochemistry with immunocytochemistry can elucidate catecholamine-peptide relationships. Gelatin-ink perfusion used with fluorescence histochemistry permits the investigation of neuro-vascular relationships and documentation of vascular and parenchymal compartmentation of innervation. Combined use of fluorescence histochemistry and retrograde tracing methods demonstrates the specific cellular sources of innervation of target regions. Micropunch neurochemical analysis provides quantitative data for correlation with fluorescence histochemistry within a target region of innervation, and microspectrofluorometric analysis provides a semi-quantitative evaluation of the amount of fluorophore within a target region or within specific subcellular compartments such as the cell body or terminals.

Adrenergic control of circulating lymphocyte subpopulations. Effects of congestive heart failure, dynamic exercise, and terbutaline treatment

The current studies were undertaken to explore the relationship between enhanced sympathetic nervous activity and lymphocyte subset distribution in three settings: congestive heart failure, dynamic exercise, and beta-adrenergic agonist treatment. We compared the number and subset distribution of circulating lymphocytes in 36 patients with congestive heart failure and 31 age-matched control subjects. The number of circulating lymphocytes was lower in heart failure than in control. This was due to a reduction in Tsuppressor/cytotoxic and natural killer cells without significant alteration of Thelper cells. The extent of the alteration was similar in patients with idiopathic and ischemic heart failure, but the reduction was more pronounced in patients with New York Heart Association class III-IV than in class I-II. The plasma catecholamine elevation in heart failure was also independent of etiology but more pronounced in the more severely ill patients. We also assessed lymphocyte subsets after acute stimulation of sympathetic activity by dynamic exercise and after treatment with the beta-adrenergic agonist terbutaline. Dynamic exercise until exhaustion increased the number of circulating lymphocytes in healthy controls and heart failure patients in a subset-selective manner. By contrast, a 7-d treatment with terbutaline caused a reduction in the circulating number of lymphocytes in some subsets that was identical to that seen in heart failure patients. We conclude that prolonged sympathetic activity reduces the number of circulating lymphocytes by a beta-adrenergic mechanism. Such alterations might be involved in the pathophysiology of heart failure and other disease states involving increased activity of the sympathetic nervous system.

Splenic noradrenergic and adrenocortical responses during the preclinical and clinical stages of adoptively transferred experimental autoimmune encephalomyelitis (EAE)

When experimental autoimmune encephalomyelitis (EAE) is induced by adoptive transfer of myelin basic protein (MBP)-specific lymphocytes the splenic noradrenergic and adrenocortical responses mirror in most respects those that occur following sensitization with spinal cord and Freund's adjuvant (CFA), despite the absence of the primary immune challenge. An early drop in splenic noradrenaline (NA), observed only when purified protein derivative-primed cells are transferred may reflect a vigorous proliferative response in vitro, not observed with MBP-specific cells. However, serum corticosterone (CS) levels and the density of splenocyte beta-adrenergic receptors were increased in both experimental groups within 3 days of cell inoculation. The stress of clinical signs of EAE resulted in highly significant increases in both splenic NA and plasma CS. Thus adoptively transferred EAE provides a well-delineated model of autoimmune disease for investigating the immunomodulatory role of the neural and endocrine systems.

Psychosocial effects on immune function: neuroendocrine pathways

Psychoneuroimmunology represents the newest interdisciplinary endeavor relevant to psychosomatic medicine. Work in this area is particularly exciting because it promises to reveal a more unified view of the individual and the complex interactions between social, psychological, neural, endocrinological, immunological, and genetic factors that contribute to disease. This article reviews the major biological pathways implicated in the psychosocial modulation of immune function and disease resistance.

Mitigation of beta 1- and/or beta 2-adrenoceptor function in human heart failure

1. Patients with congestive heart failure (CHF) have an elevated activity of the sympatho-adrenal system. We have investigated several aspects of beta-adrenoceptor desensitization in such patients. 2. The positive inotropic response to isoprenaline was attenuated in CHF patients, and the pD2-values for isoprenaline's positive inotropic effect gradually decreased in more severe forms of the disease. Stimulation of adenylate cyclase by isoprenaline was also mitigated in cardiac membranes from patients with CHF. 3. We then studied the density of cardiac beta 1- and beta 2-adrenoceptors in order to understand the mechanism of beta-adrenoceptor desensitization in these patients. Our data show that cardiac beta 1-adrenoceptors are down-regulated in all forms of severe CHF, but that cardiac beta 2-adrenoceptor density decreases only in some forms of CHF including ischaemic cardiomyopathy and mitral valve disease. 4. In circulating mononuclear leucocytes (MNL) obtained from CHF patients at rest, isoprenaline- and prostaglandin E1-stimulated cAMP generation as well as cholera toxin and pertussis toxin catalyzed ADP ribosylation were similar to those in MNL from control patients. However, pretreatment of intact MNL with pertussis toxin enhanced cAMP generation in CHF patients but not in healthy control subjects, suggesting a tonic inhibitory effect of Gi in such patients. 5. We conclude that alterations of adrenoceptors and of their signal transduction might contribute to the desensitization of beta-adrenergic responses in CHF.

A role for the autonomic nervous system in modulating the immune response during mild emotional stimuli

The role of the autonomic nervous system in the modulation of the immune response to emotional stimuli, was established in rats subjected to the passive avoidance test. An increase in splenic primary antibody response directed against SRBC was found after exposure of rats to the passive avoidance apparatus (novelty). Both local surgical denervation of the spleen and beta-receptor blockade (timolol, 1 mg/kg i.p. 1 h prior to testing) prevented the increase in primary antibody response.

Lactational alcohol exposure elicits long-term immune deficits and increased noradrenergic synaptic transmission in lymphoid organs

Increasing evidence suggests that the sympathetic nervous system plays an important role in immunomodulation. While chronic alcohol consumption has been associated with immune deficits, the effects of exposure to alcohol during early postnatal life on subsequent immunocompetence and activity of sympathetic neurons in lymphoid organs are not known. This study examined the long-term effects of lactational alcohol consumption on cellular immune responses and noradrenergic synaptic transmission in lymphoid and other organs of the young adult C57BL/6 mouse. The data show that exposure to alcohol via the mother's milk was associated with long-term deficits in cellular immunity, including suppression of the local graft vs host and contact hypersensitivity responses. The animals also displayed enhanced noradrenergic synaptic transmission and decreased beta-adrenoceptor density selectively in lymphoid organs. These neuroimmune changes are particularly striking since body weight-gain of the suckling pups was normal and their blood alcohol concentration was considerably lower than that of the alcohol-consuming dam. This suggests an increased sensitivity of the nascent immune and nervous systems during the critical period of early postnatal development.

Kinetic analysis of K+ ion channel function in lymphokine-activated killer (LAK) cells

K+ ion channels of lymphocytes have been implicated in cellular differentiation, activation and cytolytic functions. We previously demonstrated that K+ channel blockers modulate lytic activity of CTLs and LAK cells. In the present study, we define and quantitate the inhibitory effects of ion channel blockers on the lytic process using kinetic analysis of lysis. The K+ channel blocker, 4-aminopyridine, the neuroendocrine monoamine, serotonin, its agonist, quipazine, and the Ca++ dependent K+ channel blocker, quinidine were found to non-competitively inhibit the lytic process in a dose-dependent manner. These compounds inhibit lytic activity by causing a decrease in the maximum velocity (Vmax) by which LAK cells lyse tumor targets. These ion channel blockers did not alter effector or target cell viability or the binding of LAK cells to tumor cells. The inhibitory effects occurred at the effector cell level, since preincubation of LAK effector cells resulted in a dose-dependent decrease in Vmax which was related to a slower rate of target cell lytic programming (k2) by the LAK effector cells. Modulation of LAK cell lytic function occurs at a post-binding step, perhaps in the generation or release of the lytic signal.

Beta-adrenoceptor control of immune function in congestive heart failure

1. We have determined the number of beta-adrenoceptors and the isoprenaline-stimulated cAMP generation in lymphocyte subsets. The in vitro beta-adrenergic sensitivity was greatest in Tsuppressor/cytotoxic- and natural killer cells and smallest in Thelper- and B-cells. B lymphocytes appear to have a poor receptor coupling to adenylate cyclase as they have many beta-adrenoceptors but generate only little cAMP in response to isoprenaline. 2. A 7 day treatment of healthy volunteers with terbutaline decreased the number of circulating cells in those lymphocyte subsets with a high in vitro sensitivity to beta-adrenoceptor stimulation (i.e. Tsuppressor/cytotoxic- and natural killer cells) but not in those with a poor in vitro sensitivity (i.e. Thelper- and B-lymphocytes). 3. Similar alterations of circulating lymphocyte subsets were found in patients with congestive heart failure (CHF). These alterations were not related to the aetiology of CHF but to its severity and could be correlated with plasma catecholamine levels. 4. We conclude that prolonged exposure to beta-adrenoceptor agonists or enhanced sympathetic activity can decrease the number of circulating lymphocytes with an increase in the Thelper-/Tsuppressor/cytotoxic-cell ratio.

Prenatal ethanol exposure alters immune capacity and noradrenergic synaptic transmission in lymphoid organs of the adult mouse

Clinical and experimental evidence indicates that exposure to alcohol in utero is associated with altered immune capacity. The mechanisms underlying such abnormalities are not clear. However, the suggestion that reciprocal interactions between the immune and the nervous systems are necessary for a competent immune response may be relevant. This work examined the consequences of prenatal ethanol exposure on cellular immune responses and noradrenergic synaptic transmission in lymphoid organs of the adult C57B1/6 mouse. Pregnant mice were fed a liquid diet containing 25% of the calories as ethanol (4.8% w/v) or pair-fed an isocaloric equivalent of this diet throughout gestation, followed by foster-nursing the neonates on normal dams. As young adults, mice exposed to ethanol prenatally displayed immunologic and selective neurochemical changes: (1) depressed ability to produce cellular immune responses, including contact hypersensitivity and a local graft-vs-host response, and (2) altered noradrenergic synaptic transmission, including enhanced norepinephrine turnover, and a reduction in norepinephrine levels and beta-adrenoceptor density in the thymus and spleen, but not the heart. However, both the integrity and compartmentation of noradrenergic nerve fibres in the spleen were intact. It is suggested that altered noradrenergic synaptic transmission selectively in lymphoid organs may contribute to the impaired immune capacity associated with fetal alcohol exposure.

Catecholamines increase lymphocyte beta 2-adrenergic receptors via a beta 2-adrenergic, spleen-dependent process

We investigated the mechanisms underlying the increase in mononuclear leukocyte (MNL) beta 2-adrenergic receptor (AR) number and responsiveness after acute infusion of catecholamines. Infusion of isoproterenol and epinephrine, but not of norepinephrine, acutely increased MNL beta-AR density, and this was blocked by the beta 2-selective antagonist ICI 118,551 but not by the beta 1-selective antagonist bisoprolol, suggesting a beta 2-AR-mediated effect. Infusion of isoproterenol but not of norepinephrine also induced a lymphocytosis, with an increase in the number of circulating suppressor/cytolytic T (Ts/c)- and natural killer (NK)-cells but a decrease in helper T (Th)-cells, leading to a decreased Th-Ts/c-cell ratio. beta-AR density was higher in Ts/c-cells than in Th-cells. After isoproterenol infusion, beta-AR density was elevated in all lymphocyte subsets but not in monocytes or platelets, suggesting a lymphocyte-specific phenomenon. Infusion of isoproterenol in splenectomized patients did not alter lymphocyte subset composition and only slightly increased beta 2-AR density. In healthy subjects lymphocyte proliferation in response to various mitogens was attenuated after infusion of isoproterenol but not of norepinephrine; this effect was abolished in splenectomized patients. We conclude that the elevated MNL beta-AR density after acute exposure to beta-adrenergic agonists is caused by a release of lymphocyte subsets from the spleen into the circulation and/or by an exchange of lymphocyte subsets between the spleen and the circulation, whereby freshly released splenic lymphocytes appear to carry more beta-AR than those found in the circulation. This appears to impair immune responsiveness in a dual manner, by decreasing the Th-/Ts/c-cell ratio and by rendering lymphocytes more sensitive to the antiproliferative effects of catecholamines via a higher beta-AR density.

Origin of noradrenergic innervation of the spleen in rats

Noradrenergic (NA) sympathetic innervation of the spleen was examined in young adult Sprague-Dawley rats (200-250 g) following surgical removal of the superior mesenteric-celiac ganglia (SM-CG) and/or bilateral transection of the subdiaphragmatic vagus nerve. Sham-operated and unoperated rats served as controls. NA sympathetic innervation of spleens from sham-operated and unoperated controls, and from vagotomized rats, was qualitatively similar, with fibers distributing to the capsule, trabeculae, vasculature, and parenchyma of the white pulp. Complete ganglionic extirpation resulted in almost total denervation of NA fibers in all compartments of the spleen. High-performance liquid chromatography with electrochemical detection (LCEC) for catecholamines (CA) and quantitative morphometry of the density of NA varicosities confirmed these observations. LCEC revealed a greater than 85% depletion of norepinephrine (NE) in the spleen following superior mesenteric-celiac ganglionectomy. Stereological evaluation of NA varicosities with a point counting method revealed a decline of 99% in the volume density of NA terminals that occurred uniformly in all compartments of spleens from ganglionectomized rats. In addition, stereological analysis revealed a loss of total NA varicosities (approximately 31% decrease) in spleens from sham-operated rats. This loss in volume density occurred largely due to a loss in parenchymal fibers (approximately 45% decrease). Bilateral subdiaphragmatic vagotomy blocked the effect on NA innervation produced by the surgical stress of sham operation. Retrograde tracing following injection of either fluorogold or true blue into the spleen, coupled with immunocytochemical localization of tyrosine hydroxylase (TH), demonstrated abundant fluorogold (true blue)-labeled neurons in the SM-CG; many, but not all, of these neurons also were TH-positive. These findings indicate that the SM-CG neurons supply NA innervation to the spleen, providing sympathetic innervation as the second neuron in the classical two-neuron sympathetic chain, and suggest additional non-NA innervation of the spleen as well. This study also suggests that surgical stress of sham operation may alter directly the NA innervation of the spleen, possibly by inducing temporary retraction of NA fibers of the parenchymal compartment, which is likely to reduce the availability of NE for interaction with cells of the immune system that possess adrenoceptors and are present adjacent to NA varicosities in this region.4+ Bilateral vagotomy ameliorated the effects of sham operation on NA innervation; since the vagal nerve does not distribute fibers to the spleen, this effect is likely to occur through altered feedback circuits effecting sympathetic outflow, or through altered neuroendocrine outflow.(ABSTRACT TRUNCATED AT 400 WORDS)

Autonomic innervation of the spleen of the coho salmon, Oncorhynchus kisutch. a histochemical demonstration and preliminary assessment of its immunoregulatory role

Regulation of immunity by the nervous system, now a well-established phenomenon in mammals, is effected in part through the autonomic innervation of lymphoid tissues. Noradrenergic fibers specifically target lymphocyte-rich areas in mammalian lymphoid tissues, and their ablation, or the administration of adrenergic agents, can significantly alter immune responses. This study demonstrates that the spleen of the coho salmon is also richly innervated by adrenergic neurons. While this innervation enters the spleen and remains largely associated with the splenic vasculature, fibers can also be observed entering the parenchyma. Although the coho spleen does not possess a well-developed white pulp, aggregations of leukocytes are found adjacent to the major blood vessels in close proximity to the vascular nervous tissue and parenchymal fibers. Chemical sympathectomy with 6-hydroxydopamine results in a significant enhancement of the splenic antibody-secreting cell response to trinitrophenylated sheep red blood cells. These results suggest that sympathectomy is removing a constraint, in the form of inhibitory catecholamines, on the immune response. The potential benefits from a teleost model of neural-immune interactions are discussed.

Innervation of the spleen in the rat: evidence for absence of afferent innervation

Catecholaminergic fibers in the spleen have been well characterized in the rat and this innervation is believed to be an important source of modulation of the immune system. The presence or role of afferent feedback from the spleen has not been systematically investigated. We have examined whether the spleen receives afferent innervation from sensory ganglia and also have assessed the sources of efferent innervation to the spleen in the rat. The fluorescent retrograde anatomical tracers fluoro-gold (FGo) or fast blue (FB) were injected into the spleens of adult female rats and dorsal root, sympathetic chain, nodose, and celiac-mesenteric plexus ganglia were collected. In additional animals, the spleen was either injected with the anatomical tracer wheat germ agglutinin-horseradish peroxidase (WGA-HRP) or else regular HRP was applied to the cut end of the splenic nerve. Also, we examined the effects of cutting the splenic nerve on the retrograde labeling of cell bodies in the ganglia and on the catecholamine histochemistry of the spleen. The neuroanatomical results were based primarily upon the tracer FGo and verified that the celiac-mesenteric plexus ganglia provide a major efferent input to the spleen. Furthermore, lower thoracic sympathetic chain ganglia provide an additional and substantial efferent supply to the spleen. Cutting of the splenic nerve prevented retrograde labeling of cell bodies in the celiac-mesenteric plexus ganglia and sympathetic chain ganglia of rats injected with tracers into the spleen and also eliminated catecholamine histofluorescence in the spleen. In terms of afferent labeling, the results with FGo indicated that there were no cell bodies labeled in afferent ganglia following splenic injections.(ABSTRACT TRUNCATED AT 250 WORDS)

The beta-adrenergic agonist isoproterenol suppresses experimental allergic encephalomyelitis in Lewis rats

Treatment with the beta-adrenergic agonist isoproterenol suppresses clinical and histological experimental allergic encephalomyelitis in Lewis rats. The effect of isoproterenol treatment is greater when the drug is given from the time of immunization through the acute phase of the illness or from 8 to 14 days post-immunization than when given for the first 7 days after immunization.

Interferon-gamma-like immunoreactivity in certain neurons of the central and peripheral nervous system

Interferon-gamma (IFN-gamma) has many important immunoregulatory functions. It has previously been presumed to be produced by activated lymphoid cells alone. The present study concerning the identification of IFN-gamma in neurons was initiated against the background that nerve function influences immunological events during inflammatory diseases. Furthermore, the immune system and the nervous system may have certain signal molecules as well as certain cell surface receptors in common. Neuronal IFN-gamma-like immunoreactivity (IFN-gamma-LI) was studied in frozen sections of rat tissues employing both rabbit polyclonal antiserum as well as seven different mouse monoclonal antibodies (mAbs) reactive with different epitopes of rat IFN-gamma. The polyclonal antiserum and three of the mAbs (DB-1, DB-14, and DB-16) showed IFN-gamma-LI in neurons. DB-1, the most extensively studied mAb, stained distinct networks of nerve terminal-like profiles both in the brain and spinal cord. Also, scattered brain neuronal cell bodies showed IFN-gamma-LI as well as a subpopulation of primary sensory ganglion cells and their intra CNS terminals. In addition, IFN-gamma-LI was also detected in nerve terminal-like profiles in skin, gut, and lymphoid organs. Terminals were especially prominent around blood vessels. We propose that IFN-gamma has a role in cell interactions not only in the immune system but also in the nervous system as well as in interactions between the nervous and immune systems.

Neurotransmitter-lymphocyte interactions: dual receptor modulation of lymphocyte proliferation and cAMP production

Stimulation of the beta-adrenergic receptor on lymphocytes can decrease the proliferative response of these cells to mitogens. We have found that simultaneous stimulation of T cells with the beta-adrenergic agonist isoproterenol and mitogens (phytohemagglutinin (PHA) and OKT3 monoclonal antibody) results in a 2- to 4-fold increase in cAMP production compared to cells exposed to isoproterenol alone. Mitogens alone have little effect on cAMP synthesis, but do activate the phosphatidylinositol (PI) cycle, suggesting that interactions may be occurring between the second messenger systems resulting in a cAMP synergy. Further experiments suggest that calcium may be involved in inducing the cAMP synergy observed in T cells. It is proposed that the synergy between beta-adrenergic and mitogenic stimulation of T cells for cAMP may be involved in the mechanism of catecholamine modulation of lymphocyte function.

Social confrontation "stress" in aggressive fish is associated with an endogenous opioid-mediated suppression of proliferative response to mitogens and nonspecific cytotoxicity

We have previously shown that social confrontation between aggressive fish (e.g., Tilapia) produces a suppression of several immunological parameters--nonspecific cytotoxicity and mitogen-stimulated proliferation in pronephric leukocytes--in the subordinate fish. By using the opioid antagonist, naltrexone, we now demonstrate indirectly that this immunosuppression is in part mediated by the endogenous opioid system. Evidence is presented that naltrexone-mediated reversal of immunosuppression may be limited to the populations of the cytotoxic and T-cell lineages. The proliferation response to lipopolysaccharide is unaffected by naltrexone. Our data also demonstrate that serum from subordinate (immunosuppressed) fish is immunosuppressive in normal fish--an effect that can be reversed by naltrexone. These results support a link between the neuroendocrine and immune systems in fish, the lowest vertebrate.

Conditioned immune responses and pharmacotherapy

Data on the conditioned modulation of immune responses are briefly reviewed, and the successful application of conditioning operations to the pharmacotherapy of autoimmune disease in lupus-prone mice is described. These data provide the background for a discussion of the role of conditioning in pharmacotherapy and an experimental analysis of the "placebo effect" as a conditioned response.

Intracerebroventricular infusion of interleukin 1 rapidly decreases peripheral cellular immune responses

Low doses (50-200 pg or 3.1-12.4 fmol) of interleukin 1 (IL-1) infused into the brain of rats produced rapid suppression of various cellular immune responses in peripheral lymphocytes of rats. Fifteen minutes after infusion of purified IL-1 beta into the lateral ventricle, natural killer cell activity, response to phytohemagglutinin stimulation, and interleukin 2 production were markedly suppressed in lymphocytes isolated from blood and spleen. These effects were due to infusion of IL-1 into brain since they did not occur when IL-1 was infused into the cisterna magna (essentially posterior to brain) or was injected intraperitoneally. Effects of IL-1 in brain could be blocked by simultaneous infusion of alpha-melanocyte-stimulating hormone, which is known to block the biological actions of IL-1. To stimulate release of endogenous IL-1 in brain, lipopolysaccharide was infused; this produced similar effects as IL-1, and these effects also were blocked by alpha-melanocyte-stimulating hormone. At longer intervals after infusion of IL-1 and lipopolysaccharide (3, 6, and 24 hr), immune responses returned to baseline or remained suppressed; i.e., "rebound" immunopotentiation did not occur. Finally, IL-1 infusion suppressed cellular immune responses in adrenalectomized animals, thereby showing that the effects of central IL-1 on peripheral cellular immune responses were, at least in part, independent of the stimulatory effect of IL-1 on secretion of adrenal hormones. These results indicate a link from brain to peripheral immune responses by means of action of a cytokine acting in the brain.

Local enhancement of major histocompatibility complex (MHC) class I and II expression and cell infiltration in experimental allergic encephalomyelitis around axotomized motor neurons

The effect of unilateral peripheral nerve lesions on the inflammatory response of experimental allergic encephalomyelitis (EAE) in rat central nervous system (CNS) was studied. Immunostaining for major histocompatibility complex (MHC) antigens and T-cell subsets demonstrated that MHC class I expression was markedly enhanced in as well as around axotomized motor neurons and that MHC class II expression was induced on several cells, probably microglial cells, in close proximity to the axotomized motor neurons. There was also a pronounced increase in interleukin 2 receptor-positive lymphocytes as well as T-cells and the T-cell subsets on the injured as compared to the non-injured contralateral side. These effects were present particularly in the initial phase of EAE and persisted for several weeks. The results suggest that neurons may communicate immunoregulatory signals to their microenvironment and that retrograde axonal signals from the distant periphery may alter the immune response locally within the CNS.