Social temperament and lymph node innervation

Socially inhibited individuals show increased vulnerability to viral infections, and this has been linked to increased activity of the sympathetic nervous system (SNS). To determine whether structural alterations in SNS innervation of lymphoid tissue might contribute to these effects, we assayed the density of catecholaminergic nerve fibers in 13 lymph nodes from seven healthy adult rhesus macaques that showed stable individual differences in propensity to socially affiliate (Sociability). Tissues from Low Sociable animals showed a 2.8-fold greater density of catecholaminergic innervation relative to tissues from High Sociable animals, and this was associated with a 2.3-fold greater expression of nerve growth factor (NGF) mRNA, suggesting a molecular mechanism for observed differences. Low Sociable animals also showed alterations in lymph node expression of the immunoregulatory cytokine genes IFNG and IL4, and lower secondary IgG responses to tetanus vaccination. These findings are consistent with the hypothesis that structural differences in lymphoid tissue innervation might potentially contribute to relationships between social temperament and immunobiology.

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.

Stress-induced remodeling of lymphoid innervation

Lymphoid organs have long been known to harbor neural fibers from the sympathetic division of the autonomic nervous system, but recent studies suggest a surprising degree of plasticity in the density of innervation. This review summarizes data showing that behavioral stress can increase the density of catecholaminergic neural fibers within lymphoid organs of adult primates. Stress-induced neural densification is associated with increased expression of neurotrophic factors, and functional consequences include alterations in lymph node cytokine expression and increased replication of a lymphotropic virus. The finding that behavioral stress can tonically alter lymph node neural structure suggests that behavioral factors could exert long-term regulatory influences on the initiation, maintenance, and resolution of immune responses.

Immmunohistochemical study of the blood and lymphatic vasculature and the innervation of mouse gut and gut-associated lymphoid tissue

The blood and lymphatic vascular system of the gut plays an important role in tissue fluid homeostasis, nutrient absorption and immune surveillance. To obtain a better understanding of the anatomic basis of these functions, the blood and lymphatic vasculature of the lower segment of mouse gut and several constituents of gut-associated lymphoid tissue (GALT) including Peyer's patch, specialized lymphoid nodules in the caecum, small lymphoid aggregates and lymphoid nodules in the colon were studied by using confocal microscopy. Additionally, the innervation and nerve/immune cell interactions in the gut and Peyer's patch were investigated by using cell surface marker PGP9.5 and Glial fibrillary acidic protein (GFAP). In the gut and Peyer's patch, the nerves have contact with B cell, T cell and B220CD3 double-positive cells. Dendritic cells, the most important antigen-presenting cells, were closely apposed to some nerves. Some dendritic cells formed membrane-membrane contact with nerve terminals and neuron cell body. Many fine nerve fibres, which are indirectly detected by GFAP, have contact with dendritic cells and other immune cells in the Peyer's patch. Furthermore, the expression of Muscarinic Acetylcholine receptor (subtype M2) was characterized on dendritic cells and other cell population. These findings are expected to provide a route to understand the anatomic basis of neuron-immune regulation/cross-talk and probably neuroinvasion of prion pathogens in the gut and GALT.

Autoimmune disease and innervation

In the decades before 1987, most of the research devoted to neuronal innervation was carried out in primary and secondary lymphoid organs at very different locations. This was an important period in order to understand hard-wiring of immune organs in physiology. Between 1988 and 1997, with the appearance of specific antibodies against neuronal markers, innervation was studied in inflamed tissue of patients and of animals with autoimmune diseases. This period clearly revealed that nerve fibers of, both, the sympathetic and sensory nervous system are altered, but only small amounts of tissue have been investigated by qualitative but not quantitative techniques. Between 1998 and 2007, with the understanding that sympathetic and sensory neurotransmitters might play opposite roles in inflammation, nerve fibers of the different nervous systems have been studied in parallel using quantitative techniques. These studies have been carried out in a large number of patients with long-standing autoimmune diseases. It turned out that sympathetic nerve fibers are lost in chronically inflamed tissue, while substance P-positive nerve fibers sprout into the inflamed area. This might be important because high concentrations of sympathetic neurotransmitters are antiinflammatory whereas substance P has a proinflammatory role. The first challenge for future research is the determination of innervation in the early human autoimmune disease. The second challenge is the identification of reasons for the differential loss of sympathetic in relation to sensory nerve fibers. It might well be that nerve repellent factors specific for the sympathetic nerve fiber might play an important role for the observed differential loss. Whether, or not, a therapy can be based on these findings remains to be established.

A fundamental bimodal role for neuropeptide Y1 receptor in the immune system

Psychological conditions, including stress, compromise immune defenses. Although this concept is not novel, the molecular mechanism behind it remains unclear. Neuropeptide Y (NPY) in the central nervous system is a major regulator of numerous physiological functions, including stress. Postganglionic sympathetic nerves innervating lymphoid organs release NPY, which together with other peptides activate five Y receptors (Y1, Y2, Y4, Y5, and y(6)). Using Y1-deficient (Y1(-/-)) mice, we showed that Y1(-/-) T cells are hyperresponsive to activation and trigger severe colitis after transfer into lymphopenic mice. Thus, signaling through Y1 receptor on T cells inhibits T cell activation and controls the magnitude of T cell responses. Paradoxically, Y1(-/-) mice were resistant to T helper type 1 (Th1) cell-mediated inflammatory responses and showed reduced levels of the Th1 cell-promoting cytokine interleukin 12 and reduced interferon gamma production. This defect was due to functionally impaired antigen-presenting cells (APCs), and consequently, Y1(-/-) mice had reduced numbers of effector T cells. These results demonstrate a fundamental bimodal role for the Y1 receptor in the immune system, serving as a strong negative regulator on T cells as well as a key activator of APC function. Our findings uncover a sophisticated molecular mechanism regulating immune cell functions that can lead to stress-induced immunosuppression.

Cholinergic staining of bronchus- associated lymphoid tissue

The cholinergic staining of human bronchus-associated lymphoid tissue (BALT) was studied in humans. Morsels of the human lung (containing BALT) were harvested, after having obtained the appropriate approvals, during autopsies in 24 human subjects. The samples were stained by means of the enzymatic technique of acetylcholinesterase (AChE) and/or the monoclonal immunohistochemical method of choline acetyltransferase (ChAT). A morphometrical analysis was performed by means of quantitative analysis of images and statistical analyses of the data. AChE and proteins were also measured by biochemical assay. Our results demonstrate that both AChE and ChAT are localized in the BALT of young and old humans. These enzymes undergo age-related changes. The biochemical values of AChE are as follows: 22.3 +/- 2.5 international units in young subjects and 78.5 +/- 1.9 international units in old ones. The morphometrical values of AChE confirm the biochemical ones. The morphometrical data for ChAT are 31.6 +/- 1.4 conventional units in young subjects and 71.2 +/- 1.5 conventional units in old ones. Further results are needed to draw definite conclusions concerning the location and the distribution of these two enzymatic activities in BALT. In our opinion, the presence of AChE and ChAT in BALT can be both 'non-neuronal', with a role in general metabolism, and/or 'neuronal' with a role in neuroimmunomodulation.

Dopamine nerve fibres and related receptors in bronchus-associated lymphoid tissue (BALT)

Age-related changes of the dopamine nerve fibres of bronchus associated lymphoid tissue (BALT) were investigated in male Wistar rats of 3 months (young), and 24 months (old/aged). Dopamine histofluorescence techniques have been used, associated with image analysis for the detection of dopamine nerve fibres. In young rats, white, fluorescent nerve fibres supply BALT. This tissue is innervated by a delicate network of nerve fibres rich in varicosities. In old rats these fluorescent nerve fibres are strongly reduced. Moreover, dopamine D1a and D1b receptors were stained using fluorescent monoclonal antibodies. The BALT of young rats possesses a higher number of D1a and D1b receptors, while, in the old rats, these receptors are strongly reduced. The possible significance of reduced dopamine neurotransmission in BALT of aged rats is discussed.

Catecholaminergic nerve fibers in bronchus-associated lymphoid tissue: age-related changes

Age-related changes of the catecholaminergic nerve fibers of the trachea, bronchial smooth muscle, lung capillaries and bronchus-associated lymphoid tissue (BALT) were studied in male Wistar rats aged 3 months (young), 12 months (adult) and 24 months (old/aged). Catecholamine histo- and immuno-fluorescence techniques were used, associated with image analysis and high pressure liquid chromatography with electrochemical detection of nor-epinephrine (nor-adrenaline). In young rats, blue-green fluorescent nerve fibers supply the trachea-bronchial smooth muscle and tracheal and bronchial glands. These structures are innervated by a delicate network of nerve fibers, being rich in varicosities. Pulmonary capillaries are sparsely innervated. The highest nor-epinephrine concentration was found in the trachea and bronchi, followed by BALT. The density and the pattern of noradrenergic nerve fibers of the trachea-bronchial tree or of the pulmonary vessels were similar in young and adult rats. In aged rats, a loss of noradrenergic nerve fibers, involving primarily the supply to the smooth muscle of the trachea-bronchial tree, was observed. Fluorescence microscopic techniques demonstrated a higher sensitivity than nor-epinephrine assay in detecting changes of the sympathetic nerve supply of the trachea-bronchial tree, pulmonary vessels and BALT. The possible significance of reduced noradrenergic nerve supply of the trachea-bronchial-pulmonary tree in aged rats is discussed.

Cholinergic innervation of BALT (bronchus associated lymphoid tissue) in rat

The presence and distribution of acetylcholinesterase (AChE) and cholineacetyl transferase activities (Chat) were examined in the bronchus-associated lymphoid tissue (BALT) of juvenile, adult and old rats. Histoenzymatic and immunochemical methods were used in association with quantitative analysis of images and statistical analysis of the data. Our results showed that both AChE and Chat activities were primarily confined to the BALT lymphoid cells. Only a low level of activity was observed in the sub-pleural parenchyma of the lung and in the wall of the bronchus. Moreover, both AChE and Chat activities in the BALT are specifically located in the lymphoid cells. Histoenzymatic staining and corresponding values of quantitative analysis of images confirmed morphological and immunochemical results. Finally, the intensity of histoenzymatic staining for AChE and of immunochemical staining for Chat in BALT of rats strongly decreases with age. On the basis of our results we hypothesize that both AChE and Chat activities may play an important role in BALT and both these enzymes undergo specific age-related changes.

Potential Use of Drugs that Target Neural-Immune Pathways in the Treatment of Rheumatoid Arthritis and Other Autoimmune Diseases

Many autoimmune disorders share two common features, dysregulation of the immune system and stress pathways. Two stress pathways, the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system (SNS), regulate immune system responses, through release of corticosteroids and norepinephrine (NE), respectively. These neuromediators act on immune cells via specific receptors on their surface to modulate the production of key regulatory cytokines. Glucocorticoids modulate immune responses by glucocorticoid binding to cytoplasmic glucocorticoid receptors within target cells. NE regulates immune responses through interaction with plasma membrane beta- or alpha-adrenergic receptors (AR). Both NE and glucocorticoids promote humoral immunity by altering macrophages and T cell cytokine production after an antigen challenge. Glucocorticoids and NE do this by inhibiting interleukin (IL)-12, and interferon (IFN)-gamma, which drives cell-mediated immunity. Additionally, catecholamines drive humoral immunity by stimulating macrophage IL-10 production. These catecholamine effects are mediated largely via beta(2)-AR activation. Both glucocorticoids and NE inhibit inflammation. However, under some circumstances NE promotes inflammation through interaction with macrophage alpha1-AR and subsequent increases in tumor necrosis factor alpha (TNFalpha production. Although macrophages do not normally express alpha(1)-AR, expression of this receptor on macrophages and monocytes occurs in some disease states, including rheumatoid arthritis (RA). Through these mechanisms the HPA axis and the SNS influence the course and progression of RA. Thus, the HPA axis and the SNS are likely to play key roles in the pathology of RA. Furthermore, therapeutic agents targeting the neural pathways that normally regulate immune system homeostasis may prove beneficial for treating RA and other autoimmune diseases.

Immunopathogenesis of rheumatic diseases in the context of neuroendocrine interactions

Growing evidence supports the hypothesis that alterations of the stress response and interactions between the neuroendocrine and immune systems contribute to the pathogenesis of rheumatic diseases such as rheumatoid arthritis (RA). In particular, the hypothalamus-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS) are of special interest. Polymorphisms of the corticotropin-releasing hormone (CRH)-regulating region have been described recently. These polymorphisms are differentially distributed in RA patients and healthy subjects of various ethnic origin, thus supporting the hypothesis that they represent a new genetic marker for RA susceptibility. The decreased expression of beta(2)-adrenergic receptors (beta(2)-R) on lymphatic cells in rheumatic diseases like RA, together with an impaired influence of catecholamines on immune function in these patients, further underlines the concept of a dysfunction of the ANS in rheumatic diseases. Results from work in this field will provide more insight into the pathogenesis of RA and help to establish novel therapies for this chronic rheumatic disease.

Golli-myelin basic proteins delineate the nerve distribution of lymphoid organs

The golli-myelin basic proteins (MBPs) have been known to mark the nerve fiber extensions in both the peripheral nervous system (PNS) and the central nervous system. In this paper, we show that the nerve fibers revealed by neurofilament (NF) antibody staining in thymus and spleen, colocalized with golli in the capsular, trabecular (tr), and vasculature (v) systems. In the thymus, the density of these fibers was greater in the medulla than in the cortex. In the spleen, the golli immunoreactive fibers were seen within the capsule (ca), trabeculae, and along the artery tree, as well as the fine nerve fiber networks in the periarteriolar lymphoid sheath (PALS). Golli immunoreactivity appeared to colocalize with ER-TR7, a putative marker of connective tissue in lymphoid organs. However, further examination by Western blot analysis and immunohistochemistry performed on golli "knock out" mice showed that the antigens recognized by these two antibodies were different. The reason for the apparent colocalization of golli and ER-TR7 appears to be due to the close physical association of nerve fibers with connective tissue in these organs. These results suggest that golli immunoreactivity can visualize the distribution of nerve fibers in these lymphoid organs.

The sympathetic nerve--an integrative interface between two supersystems: the brain and the immune system

The brain and the immune system are the two major adaptive systems of the body. During an immune response the brain and the immune system "talk to each other" and this process is essential for maintaining homeostasis. Two major pathway systems are involved in this cross-talk: the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system (SNS). This overview focuses on the role of SNS in neuroimmune interactions, an area that has received much less attention than the role of HPA axis. Evidence accumulated over the last 20 years suggests that norepinephrine (NE) fulfills the criteria for neurotransmitter/neuromodulator in lymphoid organs. Thus, primary and secondary lymphoid organs receive extensive sympathetic/noradrenergic innervation. Under stimulation, NE is released from the sympathetic nerve terminals in these organs, and the target immune cells express adrenoreceptors. Through stimulation of these receptors, locally released NE, or circulating catecholamines such as epinephrine, affect lymphocyte traffic, circulation, and proliferation, and modulate cytokine production and the functional activity of different lymphoid cells. Although there exists substantial sympathetic innervation in the bone marrow, and particularly in the thymus and mucosal tissues, our knowledge about the effect of the sympathetic neural input on hematopoiesis, thymocyte development, and mucosal immunity is extremely modest. In addition, recent evidence is discussed that NE and epinephrine, through stimulation of the beta(2)-adrenoreceptor-cAMP-protein kinase A pathway, inhibit the production of type 1/proinflammatory cytokines, such as interleukin (IL-12), tumor necrosis factor-alpha, and interferon-gamma by antigen-presenting cells and T helper (Th) 1 cells, whereas they stimulate the production of type 2/anti-inflammatory cytokines such as IL-10 and transforming growth factor-beta. Through this mechanism, systemically, endogenous catecholamines may cause a selective suppression of Th1 responses and cellular immunity, and a Th2 shift toward dominance of humoral immunity. On the other hand, in certain local responses, and under certain conditions, catecholamines may actually boost regional immune responses, through induction of IL-1, tumor necrosis factor-alpha, and primarily IL-8 production. Thus, the activation of SNS during an immune response might be aimed to localize the inflammatory response, through induction of neutrophil accumulation and stimulation of more specific humoral immune responses, although systemically it may suppress Th1 responses, and, thus protect the organism from the detrimental effects of proinflammatory cytokines and other products of activated macrophages. The above-mentioned immunomodulatory effects of catecholamines and the role of SNS are also discussed in the context of their clinical implication in certain infections, major injury and sepsis, autoimmunity, chronic pain and fatigue syndromes, and tumor growth. Finally, the pharmacological manipulation of the sympathetic-immune interface is reviewed with focus on new therapeutic strategies using selective alpha(2)- and beta(2)-adrenoreceptor agonists and antagonists and inhibitors of phosphodiesterase type IV in the treatment of experimental models of autoimmune diseases, fibromyalgia, and chronic fatigue syndrome.

Dual role for noradrenergic innervation of lymphoid tissue and arthritic joints in adjuvant-induced arthritis

The role of noradrenergic innervation in the disease outcome of adjuvant-induced arthritis (AA) has been examined following (1) systemic administration of guanethidine and (2) local application of 6-hydroxydopamine (6-OHDA) into the lymph nodes that drain the hind limbs (DLN). Sympathetic denervation by these different neurotoxins produced directionally opposite effects on disease outcome. These conflicting findings could be explained from differential denervation of sympathetic nerves in key target tissues that result from different routes of neurotoxin administration. Alternatively, these conflicting data could be due to differences in the mechanisms by which guanethidine and 6-OHDA destroy sympathetic nerve terminals. In this study, we compared disease outcome in AA following systemic and local DLN application of 6-OHDA to determine whether the route of administration is important to the development and progression of AA. Bilateral local DLN application of 6-OHDA or vehicle was performed 1 day before injection of Freund's complete adjuvant (CFA) to induce arthritis. For systemic denervation, 6-OHDA or vehicle was given by ip injections on days 1, 3, and 5 prior to CFA challenge and then once a week. Local DLN application of 6-OHDA resulted in significant increases in dorsoplantar width in arthritic rats by 27 days following CFA treatment compared to those of non-denervated arthritic rats. In contrast, systemic denervation in arthritic rats significantly decreased dorsoplantar widths 27 days after CFA treatment compared to those in sympathetically intact arthritic animals. X-ray analysis confirmed these findings. Further, local DLN application of 6-OHDA exacerbated the disease regardless of whether the neurotoxin was administered prior to immunization with CFA or closer to the time of disease onset. Our findings indicate that the route of 6-OHDA administration for denervation of sympathetic innervation is an important parameter in determining disease outcome, presumably due to differential sympathetic denervation of target tissues that are involved in disease development and progression. 6-OHDA administration into local DLN denervated these lymph nodes, but spared sympathetic innervation of the hind limbs, a pattern of sympathetic denervation that resulted in disease exacerbation. In contrast, systemic 6-OHDA administration which denervated both the arthritic joints and the secondary lymphoid organs attenuated the severity of AA. This study supports a dual role for NA innervation in modulating the severity of AA by innervation of the arthritic joints and lymphoid organs.

Effects of L-deprenyl treatment on noradrenergic innervation and immune reactivity in lymphoid organs of young F344 rats

Sympathetic noradrenergic (NA) neuronal activities in the thymus, spleen and mesenteric lymph nodes (MLN) and immune responses in the spleen were examined in young male F344 rats treated daily with 0, 0.25 mg, or 2.5 mg/kg body weight of L-deprenyl, an irreversible monoamine oxidase-B (MAO-B) inhibitor. Rats were treated daily for 1, 15, or 30 days, and sacrificed 7 days after the last deprenyl treatment. Deprenyl treatment increased norepinephrine (NE) content in the spleen without modifying the pattern and density of NA innervation in the splenic white pulp. The concentration of NE was unaltered in the thymus, but it was increased in the MLN of deprenyl-treated rats. One day of treatment with deprenyl decreased splenic NK cell activity while 15 days of deprenyl treatment enhanced splenic NK cell activity. Deprenyl elevated Con A-induced T lymphocyte proliferation following 30 days of treatment, but did not alter spleen cell Con A-induced IL-2 production or the percentage of CD5 + T cells in the spleen. A moderate decrease in the percentage of sIgM + B cells was observed in the spleens of 15- and 30-day deprenyl-treated rats. These results suggest that deprenyl has sympathomimetic action on sympathetic NA nerve fibers in the spleen; the enhancement of NA neuronal activity may contribute to the modulation of immune responses in the spleen.

Catecholamine modulation of lymphocyte homing to lymphoid tissues

Lymphocyte migration is an essential process for immune surveillance and for promoting cell-cell interactions necessary to generate an immune response. This report examined whether catecholamine prestimulation would alter the pattern of lymphocyte homing to spleen and lymph nodes in mice as determined by tracking fluorescently labeled cells. The results of cell sorter analysis showed that catecholamine-pretreated cells had increased accumulation in spleen and lymph nodes 1 and 2 h after i.v. injection. In addition, microscopic analysis showed that labeled cells migrated from the splenic red pulp to T-cell regions of the white pulp over a 2-h time course. Within the lymph nodes, labeled cells localized predominantly to the pericortex. Additional studies examined the migration of lymphocytes to lymphoid tissues of NGF-transgenic mice that have sympathetic hyperinnervation of spleen and peripheral lymph nodes. In contrast to the studies above, migration of T-cells from control mice to lymphoid tissues of the hyperinnervated mice was not different than that in control mice in most tissues. The accumulation of lymphocytes in lymphoid tissues is a balance between the influx of newly migrated cells and efflux back into the circulation. The studies in this report lend support to other studies showing catecholamine modulation of lymphocyte migration and homing, but it is a complex process about which much has yet to be understood.

Age-associated alterations in sympathetic neural interactions with the immune system

We have examined age-related alterations in sympathetic noradrenergic (NA) innervation in primary and secondary lymphoid organs from mouse and rat. As the thymus involuted with age, the density of NA innervation and norepinephrine (NE) concentration increased markedly. Total thymic NE was not altered significantly with age, suggesting that NA innervation is maintained as the thymus involutes. In the rat spleen, NA innervation and NE concentration were diminished with age. Enhanced antibody responses and in vitro proliferation to a T-dependent protein antigen were observed following selective destruction of NA nerve fibers with the neurotoxin 6-hydroxydopamine (6-OHDA), demonstrating that the diminished NA innervation in the aged spleen is capable of signaling the immune system. Plasticity of NA nerves in old rats was demonstrated following lesioning with 6-OHDA and in intact rats treated with L-deprenyl, a monoamine oxidase B inhibitor. These age-related alterations in NA innervation of lymphoid organs occur concurrently with age-associated changes in immune function. Understanding the functional relationship between these two physiological systems in aging will contribute to a greater understanding of sympathetic nervous system regulation of immune function.

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.

Sensory innervation of conjunctival lymph follicles in cynomolgus monkeys

PURPOSE

The importance of neuroregulation of immunoresponsiveness is recognized, but little is known of the innervation of conjunctival follicles. The access and distribution of nerves in follicles of the palpebral conjunctiva were therefore studied and those of trigeminal nerve origin distinguished.

METHODS

Serial sections of follicles were prepared for light and selected sections for electron microscopy. Intracranial lesions were made in ophthalmic or both ophthalmic and maxillary nerves several days before fixation in three of the six monkeys used and their distribution in follicles identified by induced degeneration.

RESULTS

Fine nerves penetrated follicles and terminated on arterioles, smaller blood vessels, and rarely on high endothelial venules. Other nerve branches entered the follicle parenchyma, conducted, and terminating in fine reticular fibers. Many terminals were identified as autonomic on morphologic grounds. Few terminals were in direct contact with lymphocytes and none were found in germinal centers. Other fibers terminated in the follicle associated epithelium. A large fraction of the nerve displayed degenerative changes after lesions and epithelial terminals were no longer present.

CONCLUSIONS

Nerve distribution is mostly similar to that found in other lymphoid organs with the exception of the epithelial terminals, which are described for the first time in mucosa-associated lymphoid tissue and identified as sensory. Because epithelial terminals virtually were absent from the surrounding unspecialized epithelium, it is likely that those of the follicular epithelium have a specific immune system-related function. They may represent a follicle-alerting mechanism to surface stimuli.

[Stress and the immune system]

Research in psychoneuroimmunology has demonstrated that biopsychosocial factors such as psychological stress can influence the immune system. Chronic stress has been associated with the suppression of the immune function. In contrast, acute psychological stressors and physical exercise have been shown to transiently enhance immune responses. These stress effects on immunity seem to be mediated via endocrine factors, since hormones, neurotransmitters, and neuropeptides can interact with cellular components of the immune system. In summary, experimental and clinical evidence suggests a functional relationship between stress, immunity, and diseases.

Lymphocyte traffic changes induced by monolateral vagal denervation in mouse thymus and peripheral lymphoid organs

In this report we show that after monolateral vagal denervation (vagotomy), performed at the cervical level, a transient effect, lasting about 24h, was produced on lymphocyte release from mouse thymus to peripheral lymphoid organs (spleen and lymph nodes). Labelling thymocytes in situ with fluorescein isothiocyanate (FITC) we note that the export of immature cells, CD4+CD8+, double positive (DP), and double negative, CD4-CD8- (DN), from the thymus was consistently increased 24 and 48 h after vagotomy. Double staining with anti-L3T4 (CD4) and anti-mouse CD8alpha showed that the number of DP and DN cells was significantly higher in both spleen and lymph nodes of vagotomized mice compared to controls (sham-operated), whereas the percentage of CD4+CD8- and CD8+CD4-, single positives (SP), was decreased. Considering thymic cellularity and apoptotic values, we exclude the non-specific effect of stress and suggest that this phenomenon could be in part due to a transient lack of the facilitating influence exerted by vagal efferent fibers on lymphocyte traffic at the cortico-medullary junction of the thymic gland, where mature cells, SP, leave the thymus to enter systemic circulation.

NGF modulates sympathetic innervation of lymphoid tissues

Immune tissues are known to be innervated by the sympathetic nervous system, but little is known of what directs the innervation to specific tissue compartments. This report examines the sympathetic innervation of immune tissues in transgenic mice that overexpress nerve growth factor (NGF) in skin and other epithelial structures. NGF transgenic mice exhibited dramatic hyperinnervation in the splenic marginal zone, and the medulla and capsule of peripheral lymph nodes. In contrast, the transgenic mesenteric lymph nodes showed no hyperinnervation. This difference correlated with the location of these nodes; peripheral lymph nodes drain skin where the transgene was expressed while mesenteric lymph nodes drain non-transgene-expressing structures. In addition, the level of innervation correlated with the level of NGF peptide content as assayed by ELISA (3- and 13-fold increase in transgenic spleen and axillary lymph nodes, respectively; no increase in mesenteric nodes) and immunocytochemistry. RT-PCR showed that the NGF transgene was not being expressed in the immune tissues, suggesting that immune tissues can concentrate transgene-produced NGF. It was also demonstrated that the change in innervation had functional consequences. The mitogen response to concanavalin A (ConA) by spleen cells was decreased in the transgenics suggesting that elevated catecholamines or NGF can modulate the proliferative response of these cells. These mice demonstrate that NGF can modulate the sympathetic innervation and function of the immune system.

Lymphoid tissue in the kidney of the musk shrew, Suncus murinus

We describe a lymphoid tissue in the kidney of the musk shrew, Suncus murinus. An anatomically well organised lymphoid tissue, resembling the mucosa-associated lymphoid tissue, is associated with the epithelium of the renal pelvis and the ureter, respectively. Lymphoid tissue distributed along the arcuate artery and arcuate vein is not structurally organised in centre and periphery. This tissue type is most prominently developed between blood vessels. Immunocytochemistry revealed S-100-immunoreactive dendritic cells in both, structurally organised and structurally non-organised lymphoid tissues. The lymphoid tissue is innervated by neurofilament-immunoreactive nerve fibres. Some of these nerve fibres are associated with glial fibrillary acidic protein-immunoreactive structures, indicating that they are myelinated.

Catecholamine influences and sympathetic neural modulation of immune responsiveness

Primary and secondary lymphoid organs are innervated extensively by noradrenergic sympathetic nerve fibers. Lymphocytes, macrophages, and other cells of the immune system bear functional adrenoreceptors. Norepinephrine fulfills criteria for neurotransmission with cells of the immune system as targets. In vitro, adrenergic agonists can modulate all aspects of an immune response (initiative, proliferative, and effector phases), altering such functions as cytokine production, lymphocyte proliferation, and antibody secretion. In vivo, chemical sympathectomy suppresses cell-mediated (T helper-1) responses, and may enhance antibody (T helper-2) responses. Noradrenergic innervation of spleen and lymph nodes is diminished progressively during aging, a time when cell-mediated immune function also is suppressed. In animal models of autoimmune disease, sympathetic innervation is reduced prior to onset of disease symptoms, and chemical sympathectomy can exacerbate disease severity. These findings illustrate the importance of the sympathetic nervous system in modulating immune function under normal and disease states.

Morphological relationships of choleragenoid horseradish peroxidase-labeled spinal primary afferents with myenteric ganglia and mucosal associated lymphoid tissue in the cat esophagogastric junction

The goal of the present study was to gain insight into the environmental factors influencing the activity of primary spinal afferent fibers in the different layers of the esophagogastric junction of the cat and, thus, to analyze the relationships of these afferents with various cellular components. Spinal primary afferent fibers were selectively labeled by anterogradely transported choleragenoid horseradish peroxidase conjugate (B-HRP). B-HRP was injected into the thoracic dorsal root ganglion at the T8-T13 levels. 6-Hydroxydopamine-induced sympathectomy was performed prior to B-HRP injection in order to prevent otherwise unavoidable labeling of sympathetic fibers in the gut wall. Numerous labeled fibers ran between, around, and within the myenteric ganglia. Others crossed the muscle layers directly and entered the mucosa, where some ran near granulocytes and around or through solitary lymphoid follicles. Labeled fibers were observed in the squamous esophageal epithelium but not in the fundic glandular epithelium. The fibers in the myenteric area are probably connected to the muscular tension receptors that have been detected by electrophysiologic techniques. This assumption is based on the observation that only a few fibers appear to terminate in muscle layers and on the fact that the myenteric area is very narrow and subject to powerful forces. Fibers in the myenteric ganglia could be involved in local efferent functions. Fibers in the mucosa could act as nociceptors and might be involved in local immunological responses.

Noradrenergic and peptidergic innervation of lymphoid organs in the beluga, Delphinapterus leucas: an anatomical link between the nervous and immune systems

The presence of peptidergic and noradrenergic sympathetic nerve fibers in specific compartments of both primary and secondary lymphoid organs of the rodent is well established. These nerve fibers directly contact lymphocytes and macrophages, as well as vascular and trabecular smooth muscle. We investigated the noradrenergic and neuropeptide-Y innervation of lymphoid organs in the cetacean, Delphinapterus leucas (beluga whale). The spleen, thymus, tonsil, gut-associated lymphoid tissue, and assorted lymph nodes were collected from five belugas, obtained during sanctioned hunts, and processed for catecholamine fluorescence histochemistry and for tyrosine hydroxylase and neuropeptide-Y immunocytochemistry. Innervation studies revealed fluorescent nerve fibers, tyrosine hydroxylase, and neuropeptide-Y positive nerve fibers in parenchymal lymphoid compartments, where they were closely associated with cells of the immune system, and in vascular and trabecular compartments. In lymphoid zones, tyrosine hydroxylase and neuropeptide-Y positive nerve fibers were observed in the periarteriolar lymphatic sheath and marginal zone of the spleen; in the outermost portion of the cortex, the corticomedullary zone, and medulla of the lymph nodes; in the parafollicular zones, and diffuse lymphocyte layer below the epithelium of the tonsil; in the outermost portion of some thymic lobules; and in the lamina propria of the gut. These findings are similar to those described for other mammals and substantiate an anatomical link between the nervous and immune systems in the beluga, whereby central nervous system activity may influence autonomic outflow to lymphoid organs and effect immunologic reactivity.

Neuroimmune modulation: signal transduction and catecholamines

In recent years, much interest has centered on the commonalities and bi-directional interactions between the nervous system and the immune system. This review focuses on mechanisms through which, catecholamines, a class of neuro-endocrine molecules, modulate immune functions. Catecholamines can be immune suppressive and inhibit lymphocyte activation of both T and B cells as well as the generation of immune-mediated anti-tumor responses. Some of these catecholamine-regulated activities appear to be modulated through the second messenger, cyclic AMP, whereas others appear to be catecholamine-dependent but cyclic AMP independent. Further delineation of the interacting ligand-receptor complexes, populations of responding cells and signal transduction mechanisms leading to the activation of specifically involved genes and gene products, will lead to enhanced understanding of the integratory functions of the nervous system in immune responses, the biology of stress, the role of stress-associated molecular mechanisms in perturbations of physiological homeostasis and the development of a new biological psychiatry with accompanying rational therapeutic modalities.

Noradrenergic and peptidergic innervation of secondary lymphoid organs: role in experimental rheumatoid arthritis

Noradrenergic (NA) and peptidergic nerve fibres are present in both primary and secondary lymphoid organs, distributing with the vasculature, trabecular and capsular smooth muscle, and within the parenchyma among cells of the immune system. NA nerve terminals directly abut lymphocytes and macrophages in spleen and lymph nodes. In these organs, norepinephrine has fulfilled the basic criteria for neurotransmission with cells of the immune system as targets. In vitro and in vivo studies have demonstrated NA modulation of primary and secondary antibody responses, cytotoxic T cell responses, natural killer cell activity, and proliferation and differentiation of both T and B lymphocytes. Substance P (SP) has been shown to modulate inflammatory responses, lymphocyte proliferation, and other immunologic reactivity. We investigated the role of NA and SP nerve fibres within lymph nodes in experimental allergic auto-immune arthritis in Lewis rats. Denervation of NA nerve fibres in popliteal and inguinal lymph nodes with 6-hydroxy-dopamine resulted in earlier onset and enhanced severity of arthritic changes as well as inflammation in bilaterally induced experimental arthritis, while denervation of SP nerve fibres in popliteal and inguinal lymph nodes with capsaicin resulted in delayed onset and diminished severity of the inflammatory changes ipsilaterally, and prevention of contralateral arthritic changes in unilaterally induced experimental arthritis. These findings suggest that NA and SP nerve fibres in lymph nodes can modulate the time course of onset and the severity of experimental arthritis in Lewis rats. These modulatory effects are distinctly different from the effects of NA and SP nerve fibres in the joints themselves.

Central nervous system influences on lymphocyte migration

The immune response network is only one of many physiologic adaptive responses to environmental change and there is now substantial evidence that adaptive responses involving the central nervous system have an impact on immune outcome. Effective immune function depends upon a highly mobile population of precursor and effector cells of the lymphoid system. In this review it is proposed that many of the alterations in immunity resulting from CNS activity may be explained in terms of changes in lymphocyte migration patterns in response to endocrine signals, neural signals via neurotransmitter release, or direct contacts between nerves and cells of the immune system.

Innervation of lymphoid organs and implications in development, aging, and autoimmunity

We now have substantial evidence demonstrating noradrenergic sympathetic and peptidergic innervation of both primary and secondary lymphoid organs. We have established criteria for norepinephrine, and some of the neuropeptides, as neurotransmitters, and have found changes in immune responsiveness following pharmacological manipulation of noradrenergic sympathetic or peptidergic nerves. Classic receptor binding studies have demonstrated a wide variety of target cells that possess beta-adrenoceptors and receptors for neuropeptides on cells of the immune system, including lymphocyte subsets, macrophages, accessory cells, or stromal elements. In this chapter we describe noradrenergic and peptidergic innervation of primary and secondary lymphoid organs in development, at maturation and during the normal aging process, and discuss possible functional implications of direct neural signals onto cells of the immune system at critical time points in the lifespan of an animal. Further, we examine for involvement of noradrenergic sympathetic and peptidergic innervation in the development and progression of several autoimmune disorders, including adjuvant-induced arthritis, New Zealand mice strains as a model for hemolytic anemia and lupus-like syndrome, and the experimental allergic encephalomyelitis model for multiple sclerosis.

Innervation of mucosal immune cells in the gastrointestinal tract

There is mounting evidence for interactions between the immune and peripheral nervous systems. Many regulatory molecules are candidate mediators for communication between inflammatory cells and nerves; however, the extent of targeting of neurotransmitters (and interleukins) as intersystem messengers has been somewhat overlooked. Lymphoid tissues are well supplied by nerves and the gastrointestinal lamina propria, which is populated by a variety of immune cell types, is densely innervated. One-half to two-thirds of mast cells are closely apposed to nerves in the intestinal mucosa, in both rodents and humans, and nerve stimulation has been reported to cause mast cell activation. Although less extensively studied, both eosinophils and plasma cells in the gastrointestinal mucosa are also positioned for interaction with nerves, and intra-epithelial leukocytes may be subject to diffusible neurally-derived mediators. Peyer's patches are relatively sparsely innervated but appear to express neuropeptide receptors in inflammatory conditions. Although the nerves in the mucosa have traditionally been thought of as a static component, recent experiments suggest that these may undergo extensive remodelling during nematode-induced inflammation. Such data suggest a dynamic interplay between the immune and nervous systems during inflammatory episodes in the gut, although considerable work is still needed to determine the importance of neuro-immune interactions in gastrointestinal homeostasis and inflammation.

Stress--mechanisms of immunosuppression

Stress, a term commonly used to describe varied phenomena, should be restricted to describe an adaptive response by an animal to threats to homeostasis. The threats to homeostasis are called stressors. Stressors include a variety of physical, psychological, chemical, or infectious causes that are modified by intrinsic and extrinsic factors. Examples of modifiers include stressor severity, duration, novelty, host genetics and immune status. What may be a stressor to an animal in one situation, when modified, may not be a stressor in another situation. Mechanisms of stress once thought to involve a single pathway described by Seyle as the General Adaptation Syndrome, have been rejected. Four pathways, some incompletely defined, have been implicated in modulation of the immune system. They include autonomic nervous system, the hypothalamic adrenal axis, extra-adrenal pathways involving neuropeptides and neurotransmitters and neuroimmunological mediators. The mechanisms of stress-induced immunosuppression resistance are poorly defined in domestic fowl and will require careful experimentation linking defined stressors with altered physiological responses that affect specific immune function and result in increased disease susceptibility.

[The effect of in vitro X-irradiated blood transfusions on the morphostructure of immunocompetent organs and their nerve elements]

A study was made of changes that occur in the rat thymus, spleen, lymph nodes, their nerve elements, and spinal ganglia under the effect of the in vitro X-irradiated blood transfusions. Parallelism was noted in the activation of the immunocompetent organ morphostructures, the rate of reactive alterations in nerve elements, and the improvement of the immunity indices.

Peptidergic innervation of rat lymphoid tissue and lung: relation to mast cells and sensitivity to capsaicin and immunization

The peptidergic innervation of lymphoid tissue and the lung in relation to mast cells was studied in rat. The sensitivity of neuropeptide-containing nerves to capsaicin treatment and immunization was also examined. Measurements of the content of neurokinin A and calcitonin gene-related peptide revealed that the lung contained the highest content of both neuropeptides; lymph nodes had intermediate levels, whereas the spleen had the lowest content. Immunohistochemistry showed that the calcitonin gene-related peptide- and neurokinin A-immunoreactive nerves in lymph nodes were mainly found around blood vessels, whereas in the lung the nerves were present within the lining respiratory epithelium, bronchial smooth muscle, around blood vessels and close to lymphoid aggregates. Combined immunohistochemistry for serotonin (5-hydroxytryptamine), as a marker for mast cells, and tachykinins or calcitonin gene-related peptide revealed that a close association was often present between the nerves and 5-hydroxytryptamine-positive cells in the bronchi of the lung, while 5-hydroxytryptamine-positive cells were not observed in lymph nodes. The neurokinin A and calcitonin gene-related peptide content in lymph nodes, spleen and lung, but not the content of neuropeptide Y, was markedly decreased by capsaicin treatment, suggesting a sensory origin for the two former peptides. Aerosol immunization increased the levels of calcitonin gene-related peptide in the lung, whereas the content in mediastinal lymph nodes was not affected. These data demonstrate a peptidergic innervation mainly of blood vessels in lymphoid tissue and a close relation between sensory nerves and mast cells as well as lymphoid aggregates in the bronchi of the lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of peptidergic nerve fibers in rat bronchus-associated lymphoid tissue: light microscopic observations

The localization of neuropeptide Y (NPY), substance P (SP), calcitonin gene-related peptide (CGRP) and vasoactive intestinal polypeptide (VIP) in the nerve fibers of rat bronchus-associated lymphoid tissue (BALT) was investigated by light microscopic immunohistochemistry. Nerve fiber bundles revealing NPY-like immunoreactivity were shown to enter the BALT together with pulmonary artery branches. They frequently reached the central zone of the BALT to give rise to fine, tortuous fibers. On the other hand, nerve fibers immunoreactive for SP and CGRP seemed to distribute in the subepithelial zone of the BALT after dissociating from fiber networks in the walls of bronchi, although small numbers of SP and CGRP fibers were also seen in the BALT central zone. CGRP fibers formed a more intense network than SP fibers in the BALT. Scattered VIP fibers were found only in the subepithelial zone of the BALT. These findings not only suggest that the four kinds of peptidergic fibers act on BALT in multiple ways, but also that these neuropeptides may be involved in the control of mucosal immunity, lymphocyte migration and proliferation within the BALT.

Neuroimmunomodulatory interactions of norepinephrine and serotonin

Monoamine neuroleptics alter rodents responses to immunization, suggesting that norepinephrine (NE) and serotonin (5HT) are neuroimmunomodulatory in these animals. Although endocrine factors participate in their mechanism(s) of action, recent studies suggest that NE and 5HT also interact more directly with immunocompetent cells. This review provides an overview of evidence for a direct regulatory link between the nervous and immune systems and further speculates on the process by which NE and 5HT realize in part, their neuroimmunomodulatory potential. Anatomical data show that noradrenergic fibers of the sympathetic nervous system innervate lymphoid organs providing a channel of communication between neurons and lymphocytes. Presumably neural signals transmitted by NE are received by platelets that in turn, transduce them via 5HT into immunomodulatory messages. It is proposed that NE alters the capacity of platelets to sequester and/or catabolize 5HT, thus regulating its physiologically active pool in the plasma. Macrophages possess a 5HT uptake system, the kinetic properties of which make them sensitive to changes in plasma levels of the amine. Thus, through its ability to regulate plasma levels of 5HT, an immunosuppressive amine with access to macrophages, the nervous system can influence cells involved in antigen recognition. Support for this hypothetical immunomodulatory mechanism is gleaned from clinical and experimental studies. For example, individuals suffering emotional trauma are more susceptible than others to developing physical illness. It is of interest that platelet 5HT pharmacodynamics are often abnormal in patients with psychological disorders characterized by catecholamine deficits. Similar platelet changes have been achieved experimentally by treating rats with catecholamine antimetabolites. Additional support for the hypothesis derives from aging research since 'monoamine imbalance' and immune dysfunction are co-characteristics of senescence. In aging rodents and humans, central catecholamine deficits are associated with a decreased platelet affinity for 5HT and an increased plasma content of 5HT. Thus, emotional, spontaneous (age-related), or experimental changes in monoamine homeostasis have the potential to increase the risk of disease in affected individuals. Perhaps part of this effect results from endocrine perturbations associated with the trauma. However, a direct interaction between the nervous and immune systems involving monoamines is also possible, and a need for future study of this potentially significant mechanism for neuroimmunomodulation is indicated.

Noradrenergic and peptidergic innervation of lymphoid tissue

Sympathetic noradrenergic nerve fibers innervate both the vasculature and parenchymal fields of lymphocytes and associated cells in several lymphoid organs, including the thymus, spleen, lymph nodes, gut-associated lymphoid tissue (GALT), and bone marrow, in a variety of mammalian species. This innervation is both regional and specific, and generally is directed into zones of T lymphocytes and plasma cells rather than into nodular regions or B lymphocyte regions. In the thymus, noradrenergic fibers enter with nerve bundles and plexuses around blood vessels, travel into the cortex from subcapsular plexuses and with the vasculature, and branch into the parenchyma of the thymic cortex. The vasculature and parenchymal regions of both the outer and deep cortex are innervated by these fibers. In the spleen, noradrenergic fibers enter with the vasculature, travel along the trabeculae and along the branching vasculature, and are distributed mainly in the white pulp along the central artery and associated periarterial lymphatic sheath. Fibers branch from a dense plexus around the central artery and travel into the parenchyma, where they end among fields of lymphocytes and other cell types. In lymph nodes, noradrenergic fibers enter at the hilus, travel along the vasculature and in a subcapsular plexus, and branch into the parenchyma in paracortical and cortical regions, where they end among lymphocytes. In the GALT, represented in these studies by rabbit appendix, sacculus rotundus, and Peyer's patches, noradrenergic fibers enter at the serosal surface, travel longitudinally with the muscularis interna, turn radially into internodular plexuses, plunge directly through the thymus-dependent zones, and ramify profusely among lymphocytes, enterochromaffin cells, and plasma cells in the interdomal regions. In the bone marrow, noradrenergic fibers enter with blood vessels, distribute deeply into the marrow on those vessels, and branch sparsely into the substance of the marrow. Immunocytochemical observations revealed the presence of neuro-peptide-like immunoreactivity in the thymus and spleen. Vasoactive intestinal peptide (VIP)-like immunoreactivity is found in varicose profiles in the thymus within the cortex. In the spleen, immunoreactive profiles showing neuropeptide Y-like, Met-enkephalin-like, cholecystokinin-8 (CCK)-like, and neurotensin-like immunoreactivity are present along the central artery of the white pulp and its smaller branches, with only sparse fibers of most of these peptides entering the parenchyma. CCK-like profiles are present in abundance in the white pulp among parenchymal elements.(ABSTRACT TRUNCATED AT 400 WORDS)

Immune-neuroendocrine interactions

Concepts and facts concerning immune-neuroendocrine interactions are discussed. The immune response elicits endocrine, autonomic, and brain functional changes. These changes can be mediated by soluble factors released by activated immunologic cells. As a result of these immune-neuroendocrine interactions the content of powerful agents such as hormones, neurotransmitters, and neuropeptides in the microenvironment of immunologic cells is modified. This leads to external immunoregulatory signals imposed upon autoregulatory mechanisms.

Autonomic nervous system innervation of thymic-related lymphoid tissue in wildtype and nude mice

A study was undertaken to determine the source and terminal distribution of the autonomic nervous system (ANS) innervation of lymphoid tissue in the mediastinum of male and female B10 and Balb/c wildtype and syngeneic nude (nu/nu) mice. Acetylcholinesterase (AChE) histochemistry was used to localize this hydrolytic enzyme in neural tissue and glyoxylic acid fluorescent histochemistry was used to characterize catecholaminergic (CA) innervation. The thymus was innervated by AChE-positive fibers of the vagus, the recurrent laryngeal, and the phrenic nerves. Catecholaminergic innervation was derived from the stellate ganglia and other small ganglia of the thoracic sympathetic nervous system chain. Whereas intrinsic AChE-positive innervation of the thymus was evident at the cortico-medullary boundaries and under the capsule, CA innervation was observed along the trabeculae with perivascular plexuses at the cortico-medullary boundaries and interlobular septa. Free CA fibers were noted in the medulla and in the cortex, where they were often proximal to cortical autofluorescent (CAF) cells. The rudimentary thymus of the adult nude mouse received limited ANS innervation. Only a few CA or AChE-positive fibers were evident, with the majority of fibers associated with the acinar cells of the gland. Mediastinal lymph nodes in male and female wildtype mice varied in their distribution and were frequently found clustered around nerves and ganglia. The intrinsic innervation of lymph nodes by AChE-positive fibers was confined to the subcapsular marginal sinus, with a few vascular-associated fibers in the parenchyma. Catecholaminergic perivascular plexuses were present in the hilar zone, whereas some free fibers were noted under the capsule and in the parenchyma. The mediastinal lymph nodes of male and female nude mice when compared to the lymph nodes of male and female wildtype mouse were found to be increased in number and in distribution. Clusters of these lymph nodes were found in close proximity to ANS tissue. The intrinsic innervation of the nude mediastinal lymph nodes was comparable to that present in the wildtype mouse tissue. The functional implication of these data is discussed with regard to nervous:immune system interactions.

Direct contacts between nerve endings and lymphoid cells in the jugular body of Rana pipiens

The ultrastructure of contacts between nerve terminals and lymphoid cells in a lymphoid myeloid organ, the jugular body, of Rana pipiens, has been analyzed. The results are discussed emphasizing their importance for functional relationships between the neuroendocrine and lymphoid systems.

A contribution to the study of lymphopoiesis in the bursa of Fabricius in Gallus domesticus

It has been proposed that the anatomical connection between the bursa of Fabricius and the cloaca is the pathway for unknown intestinal factors which are necessary for the induction of normal bursal lymphopoiesis. It has also been suggested that normal lymphopoiesis occurs only if nerve and vascular connections are intact. Experiments were performed to test these hypotheses. To test the influence of the intestinal contents, the bursal stalk was cut on the 16th day of incubation or at hatching. In this way, contact between the bursa and the intestinal flow in embryos was avoided and bacterial contamination of the bursa at hatching was also avoided. No change in the bursal follicles was observed. To study the influence of the nervous system on bursal lymphopoiesis, the bursa was isolated from the cloaca at hatching, and by maintaining vascularization the bursa was sutured to the peritoneum of the abdominal wall after scratching the contact surfaces. Once a new vascular network was established, one fragment of bursa was completely isolated from its normal anatomical site, causing interruption of the blood vessels and nerves of the bursa. The histological appearance of the bursa was not changed. It would appear that the integrity of the anatomical relation between bursa and cloaca and an intact nerve supply is not necessary for normal lymphopoiesis to occur in the bursa of Fabricius. In contrast, sufficient vascularization appears to be essential.

[Functional morphology of the adrenergic innervation and adrenocontaining structures of the lymphoid organs]

Topography of adrenergic neural fibres and adrenodependent structures in lymphoid organs of some mammals (rat, cat, dog, guinea-pig, golden hamster) has been studied by means of Falck's method with other histochemical methods applied simultaneously. In thymus, spleen, tonsils, lymph nodes and appendix adrenergic innervation is performed at the expense of adventitial vascular plexus and some neural fibres directed towards the organs' parenchyma. In the parenchyma of the lymphoid organs some fluorescent interfollicular macrophages and intrafollicular cells with serotonin and catecholamines in their cytoplasm were detected spectroscopically. These two types of cells respond differently to increasing amount of free amines in the organism. Orthochromic mast cells and elastic fibres also possess fluoresent properties which are connected with the presence of serotonin and catecholamines in the lymphoid organs.

[Bronchial lympho-epithelial nodules in the rat. Definition and morphological characteristics in optical and electron microscopy (author's transl)]

Among the bronchial lymphoid tissue, lympho-epithelial nodules are an original component, easily distinguished from other structures, particularly from lymphoid cell infiltrates. Such structures are encountered in many species and may be characterized by a flattened epithelium, containing a few ciliated cells, devoid of mucus producing cells, and infiltrated with lymphocytes. Inter and intracellular vacuoles are described in the lympho-epithelium and the underlying mucosa. Electron microscope studies support the view that lymphoepithelium has a "trapping" function of particulate matter, more direct evidence is however attempted. Peripheral lymphatic vessels and high endothelium veins contribute to the important lymphocyte transfer. An hypothesis of capacity for antigenic recognition of the lymphoepithelial nodule is discussed.