Central CCL2 signaling onto MCH neurons mediates metabolic and behavioral adaptation to inflammation.

Sickness behavior defines the endocrine, autonomic, behavioral, and metabolic responses associated with infection. While inflammatory responses were suggested to be instrumental in the loss of appetite and body weight, the molecular underpinning remains unknown. Here, we show that systemic or central lipopolysaccharide (LPS) injection results in specific hypothalamic changes characterized by a precocious increase in the chemokine ligand 2 (CCL2) followed by an increase in pro-inflammatory cytokines and a decrease in the orexigenic neuropeptide melanin-concentrating hormone (MCH). We therefore hypothesized that CCL2 could be the central relay for the loss in body weight induced by the inflammatory signal LPS. We find that central delivery of CCL2 promotes neuroinflammation and the decrease in MCH and body weight. MCH neurons express CCL2 receptor and respond to CCL2 by decreasing both electrical activity and MCH release. Pharmacological or genetic inhibition of CCL2 signaling opposes the response to LPS at both molecular and physiologic levels. We conclude that CCL2 signaling onto MCH neurons represents a core mechanism that relays peripheral inflammation to sickness behavior.

Immunocytochemical and ultrastructural identification of adenohypophyseal cells in Ctenopharyngodon idella (Cypriniformes: Cyprinidae) during gonadal differentiation.

The adenohypophysis was studied by immunocytochemical and ultrastructural methods in juvenile grass carp (Ctenopharyngodon idella) from natural reproduction in Northern Italian rivers. The adenohypophysis included the rostral pars distalis (RPD), the proximal pars distalis (PPD) and the pars intermedia (PI), all deeply penetrated by branches of the neurohypophysis (Nh). The prolactin (PRL), adrenocorticotropic (ACTH), somatotropic (GH), thyrotropic (TSH), gonadotropic type I (GtH I) and type II (GtH II), somatolactin (SL), melanotropic (MSH) and endorphin (END) cells were identified with antisera raised against piscine and human pituitary hormones. In juveniles of 51-69 mm of total body length (TL) with undifferentiated gonads, the PRL cells, arranged in thick strands, occupied most of the RPD. The ACTH and GH cells organized in cords bordering Nh were, respectively, confined to RPD and PPD. The TSH cells were scattered among ACTH cells in RPD and among GH cells in PPD. Cells simultaneously immunoreactive to anti-follicle stimulating hormone and to anti-croaker gonadotropin were intermingled among GH and TSH cells, which were mostly in the dorsal PPD. The SL cells were detected in PI layers bordering the Nh. The MSH and END cells were intermingled in PI and, unlike what observed in other teleosts, their respective antisera did not cross-react. In individuals of 78-112 mm TL with gonads at the beginning of differentiation, the GtH II cells were detected in PPD; all other cell types increased in number. These results, supported by ultrastructural investigations, suggest that SL and GtH II cells are directly involved in gonadal differentiation in C. idella.

Increased susceptibility of melanin-concentrating hormone-deficient mice to infection with Salmonella enterica serovar Typhimurium.

Melanin-concentrating hormone (MCH) was initially identified in mammals as a hypothalamic neuropeptide regulating appetite and energy balance. However, the wide distribution of MCH receptors in peripheral tissues suggests additional functions for MCH which remain largely unknown. We have previously reported that mice lacking MCH develop attenuated intestinal inflammation when exposed to Clostridium difficile toxin A. To further characterize the role of MCH in host defense mechanisms against intestinal pathogens, Salmonella enterocolitis (using Salmonella enterica serovar Typhimurium) was induced in MCH-deficient mice and their wild-type littermates. In the absence of MCH, infected mice had increased mortality associated with higher bacterial loads in blood, liver, and spleen. Moreover, the knockout mice developed more-severe intestinal inflammation, based on epithelial damage, immune cell infiltrates, and local and systemic cytokine levels. Paradoxically, these enhanced inflammatory responses in the MCH knockout mice were associated with disproportionally lower levels of macrophages infiltrating the intestine. Hence, we investigated potential direct effects of MCH on monocyte/macrophage functions critical for defense against intestinal pathogens. Using RAW 264.7 mouse monocytic cells, which express endogenous MCH receptor, we found that treatment with MCH enhanced the phagocytic capacity of these cells. Taken together, these findings reveal a previously unappreciated role for MCH in host-bacterial interactions.

Polymorphism of somatolactin-producing cells in the goldfish pituitary: immunohistochemical investigation for somatolactin-α and -ß.

Somatolactin (SL) is a pituitary hormone belonging to the growth hormone/prolactin family of adenohypophyseal hormones. In teleost fish, SL is encoded by one or two paralogous genes, namely SL-α and -ß. Our previous studies have revealed that pituitary adenylate-cyclase-activating polypeptide stimulates SL release from cultured goldfish pituitary cells, whereas melanin-concentrating hormone suppresses this release. As in other fish, the goldfish possesses SL-α and -ß. So far, however, no useful means of detecting the respective SLs immunologically in this species has been possible. In order to achieve this aim, we raised rabbit antisera against synthetic peptide fragments deduced from the goldfish SL-α and -ß cDNA sequences. Using these antisera, we observed adenohypophyseal cells showing SL-α- and -ß-like immunoreactivities in the goldfish pituitary, especially the pars intermedia (PI). Several cells in the PI showed the colocalization of SL-α- and -ß-like immunoreactivities. Then, using single-cell polymerase chain reaction with laser microdissection, we examined SL-α and -ß gene expression in adenohypophyseal cells showing SL-α- or -ß-like immunoreactivity. Among cultured pituitary cells, we observed three types of cell: those that possess transcripts of SL-α, -ß, or both. These results suggest a polymorphism of SL-producing cells in the goldfish pituitary.

Sexual dimorphism in the effect of concomitant progesterone administration on changes caused by long-term estrogen treatment in pituitary hormone immunoreactivities of rats.

BACKGROUND: Since in clinical practice long-term estrogen (E) treatment is frequently applied, our aim was to study the effect of concomitant progesterone (P) administration on changes caused by long-term estrogen treatment in the secretion of LH, FSH, PRL and GH. MATERIAL/METHODS: Diethylstilbestrol (DES), P or both in silastic capsules were implanted under the skin of prepubertal Sprague-Dawley male and female rats. Animals survived for two or five months. We have also studied whether the changed hormone secretion caused by DES can return to normal level 1 or 2 months after removing DES capsule. RESULTS: 1.) The males more rapidly responded than females with decreasing basal LH release upon treatments. The basal FSH release was decreased only in males. The effect of DES persisted in males; however, in females basal LH and FSH levels were upregulated after removal of DES capsule. 2.) The basal GH levels were low in each group. The body weight and length were depressed by DES in both genders and P little blunted this effect. The body weight and length in males remained low after removal of DES capsule, in females it was nearly similar to intact rats. 3.) There was no sexual dimorphism in the effect of steroids on PRL secretion. In both genders DES extremely enhanced the PRL levels, P prevented the effect of DES. PRL levels returned to intact value after removal of DES influence. 4.) Removal of DES capsule reversed the changes in the immunohistochemical appearance of hormone immunoreactivities. CONCLUSIONS: There was sexual dimorphism in the change of basal gonadotropic hormone and GH secretion but not of PRL upon DES and DES+P treatments. P was basically protective and this role may be mediated by P receptors locally in the pituitary gland.

Production, characterization, and applications of mouse monoclonal antibodies against gonadotropin, somatolactin, and prolactin from common carp (Cyprinus carpio).

The gonadotropin alpha subunit (cGTH alpha), gonadotropin II beta subunit (cGTHII beta), somatolactin (cSL), and prolactin (cPRL) were isolated from the pituitaries of common carps, purified by traditional chromatographic analysis, identified by mass-chromatographic analysis, and used as immunogens in the B-lymphocyte hybridoma technique. Totally, 7, 11, 17, and 8 hybridoma cell lines were established, which were able to stably secrete monoclonal antibodies (mAbs) against cGTH alpha, cGTHII beta, cSL, and cPRL, and designated as FMU-cGTH alpha 1-7, FMU-cGTHII beta 1-11, FMU-cSL 1-17, and FMU-cPRL 1-8, respectively. The isotype, titer, and specificity were identified by enzyme-linked immunosorbent assay (ELISA), Western blot, and immunohistochemical staining, respectively, and application of these mAbs in the aforementioned tests has been proved. Furthermore, sensitive sandwich-ELISA systems for quantitative detection of the hormones mentioned above were also developed.

Melanin-concentrating hormone (MCH) modulates C difficile toxin A-mediated enteritis in mice.

OBJECTIVE: Melanin-concentrating hormone (MCH) is a hypothalamic orexigenic neuropeptide that regulates energy balance. However, the distribution of MCH and its receptor MCHR1 in tissues other than brain suggested additional, as yet unappreciated, roles for this neuropeptide. Based on previous paradigms and the presence of MCH in the intestine as well as in immune cells, its potential role in gut innate immune responses was examined. METHODS: In human intestinal xenografts grown in mice, changes in the expression of MCH and its receptors following treatment with Clostridium difficile toxin A, the causative agent of antibiotic-associated diarrhoea in hospitalised patients, were examined. In colonocytes, the effect of C difficile toxin A treatment on MCHR1 expression, and of MCH on interleukin 8 (IL8) expression was examined. MCH-deficient mice and immunoneutralisation approaches were used to examine the role of MCH in the pathogenesis of C difficile toxin A-mediated acute enteritis. RESULTS: Upregulation of MCH and MCHR1 expression was found in the human intestinal xenograft model, and of MCHR1 in colonocytes following exposure to toxin A. Treatment of colonocytes with MCH resulted in IL8 transcriptional upregulation, implying a link between MCH and inflammatory pathways. In further support of this view, MCH-deficient mice developed attenuated toxin A-mediated intestinal inflammation and secretion, as did wild-type mice treated with an antibody against MCH or MCHR1. CONCLUSION: These findings signify MCH as a mediator of C difficile-associated enteritis and possibly of additional gut pathogens. MCH may mediate its proinflammatory effects at least in part by acting on epithelial cells in the intestine.

Antipituitary antibodies in dutch patients with idiopathic hypopituitarism.

BACKGROUND: Despite extensive research, in the majority of patients with isolated growth hormone deficiency (IGHD) and multiple pituitary hormone deficiency (MPHD), the cause of their clinical picture remains unknown. Recent articles suggest that some cases of idiopathic growth hormone deficiency might be explained by a silent form of autoimmune hypophysitis based on the presence of antipituitary antibodies (APA) at high titers (>1:8). METHODS: We collected clinical data and serum from 71 patients participating in the Dutch HYPOPIT study. APA screening in 40 IGHD patients and 31 MPHD patients was performed by an indirect immunofluorescence method. APA, when present, were related to clinical and morphological pituitary findings. RESULTS: APA were present at high titers in 7 of 31 MPHD patients (23%) and 1 of 40 IGHD patients (2.5%). Among APA-positive MPHD patients, apart from growth hormone deficiency, all patients of pubertal age had gonadotroph defi- ciency, all had thyroid hormone deficiency and 50% had ACTH deficiency. CONCLUSION: The high frequency of APA in our idiopathic MPHD population indicates that, in 23% of the patients diagnosed with idiopathic MPHD, the hormone deficiencies might actually be caused by a silent form of autoimmune hypophysitis. Screening for APA should therefore be considered in all patients with 'idiopathic' MPHD.

Pituitary autoimmunity: 30 years later.

Pituitary autoimmunity encompasses a spectrum of conditions ranging from histologically proven forms of lymphocytic hypophysitis to the presence of pituitary antibodies in apparently healthy subjects. Hypophysitis is a rare but increasingly recognized disorder that typically presents as a mass in the sella turcica. It mimics clinically and radiologically other non-functioning sellar masses, such as the more common pituitary adenoma. Hypophysitis shows a striking temporal association with pregnancy, and it has been recently described during immunotherapies that block CTLA-4. Several candidate pituitary autoantigens have been described in the last decade, although none has proven useful as a diagnostic tool. This review summarizes the advances made in the field since the publication of the first review on pituitary autoimmunity, and the challenges that await clarification.

Endocrine immune interactions during chronic Toxocariasis caused by Toxocara canis in a murine model: New insights into the pathophysiology of an old infection.

Toxocara canis is the helminth causing Toxocariasis, a parasitic disease with medical and veterinary implications. Their final host are members of the family Canidae and as paratenic hosts, most of the mammals are sensitive (man, rat, mouse, among others). It has been reported that a pituitary hormone, prolactin, it is responsible for reactivation and migration of larvae to the uterus and mammary gland during the last third of gestation in bitches. In addition, this hormone has been shown to play an important role in the regulation of the immune response. Thus, the aim of this study, was to evaluate the effect of hypophysectomy in the rat model of Toxocariasis, on the immune response against this parasite during a chronic infection, for which parasite loads were analyzed in different organs (lung and brain). Furthermore, serum specific antibody titers, and percentages of different cells of the immune system were also determined. The results showed a decrease in the number of larvae recovered from lung and brain in the hypophysectomized animals. In this same group of animals, there was no production of specific antibodies against the parasite. As for the percentages of the cells of the immune system, there are differences in some subpopulations due to surgery and others due to infection. Our results demonstrated that the lack of pituitary hormones alters parasite loads and the immune response to the helminth parasite Toxocara canis.

Effect of intrahippocampal administration of anti-melanin-concentrating hormone on spatial food-seeking behavior in rats.

Melanin-concentrating hormone (MCH) is a hypothalamic peptide that plays a critical role in the regulation of food intake and energy metabolism. In this study, we investigated the potential role of dense hippocampal MCH innervation in the spatially oriented food-seeking component of feeding behavior. Rats were trained for eight sessions to seek food buried in an arena using the working memory version of the food-seeking behavior (FSB) task. The testing day involved a bilateral anti-MCH injection into the hippocampal formation followed by two trials. The anti-MCH injection did not interfere with the performance during the first trial on the testing day, which was similar to the training trials. However, during the second testing trial, when no food was presented in the arena, the control subjects exhibited a dramatic increase in the latency to initiate digging. Treatment with an anti-MCH antibody did not interfere with either the food-seeking behavior or the spatial orientation of the subjects, but the increase in the latency to start digging observed in the control subjects was prevented. These results are discussed in terms of a potential MCH-mediated hippocampal role in the integration of the sensory information necessary for decision-making in the pre-ingestive component of feeding behavior.

Thymic transcription of neurohypophysial and insulin-related genes: impact upon T-cell differentiation and self-tolerance.

The thymus is the unique lymphoid organ responsible for the generation of a diverse repertoire of T lymphocytes that are competent against non self-antigens while being tolerant to self-antigens. A vast repertoire of neuroendocrine-related genes is transcribed in the nonlymphoid cellular compartment of the thymus (thymic epithelial cells, dendritic cells and macrophages). The precursors encoded by these genes engage two types of interactions with developing T cells (thymocytes). First, they are not processed in a classical neuroendocrine way but as the source of self-antigens that are presented to pre-T cells by the major histocompatibility complex proteins of the thymus. This presentation could be responsible for the establishment of central T-cell self-tolerance to neuroendocrine functions. Second, they also deliver signal ligands that are able to bind to neuroendocrine-type receptors expressed by thymocytes. This interaction activates several types of intracellular signalling pathways implicated in the developmental process of T lymphocytes. Several experimental arguments support a role for thymic dysfunction as a crucial factor in the development of organ-specific autoimmune endocrinopathies, such as 'idiopathic' central diabetes insipidus and type 1 diabetes mellitus. The rational use of tolerogenic neuroendocrine self-antigens for the prevention/treatment of autoimmune endocrinopathies is currently under investigation.

Ghrelin-induced food intake is mediated via the orexin pathway.

The hypothalamus regulates energy intake by integrating the degree of starvation or satiation with the status of the environment through a variety of neuronal and blood-derived signals. Ghrelin, a peptide produced in the stomach and hypothalamus, stimulates feeding and GH secretion. Centrally administered ghrelin exerts an orexigenic activity through the neuropeptide Y (NPY) and agouti-related protein systems. The interaction between ghrelin and other hypothalamic orexigenic peptides, however, has not been clarified. Here, we investigated the anatomical interactions and functional relationship between ghrelin and two orexigenic peptides, orexin and melanin-concentrating hormone (MCH), present in the lateral hypothalamus. Ghrelin-immunoreactive axonal terminals made direct synaptic contacts with orexin-producing neurons. Intracerebroventricular administration of ghrelin induced Fos expression, a marker of neuronal activation, in orexin-producing neurons but not in MCH-producing neurons. Ghrelin remained competent to induce Fos expression in orexin-producing neurons following pretreatment with anti-NPY IgG. Pretreatment with anti-orexin-A IgG and anti-orexin-B IgG, but not anti-MCH IgG, attenuated ghrelin-induced feeding. Administration of NPY receptor antagonist further attenuated ghrelin-induced feeding in rats treated with anti-orexin-IgGs. Ghrelin-induced feeding was also suppressed in orexin knockout mice. This study identifies a novel hypothalamic pathway that links ghrelin and orexin in the regulation of feeding behavior and energy homeostasis.

Development of a monoclonal antibody against recombinant neuroendocrine 7B2 protein.

Mouse monoclonal antibody MON-100 was raised against the neuroendocrine protein 7B2 using bacterially produced hybrid proteins. In Western blot analysis, MON-100 reacted with 3 different 7B2 hybrid proteins and not with the respective carrier proteins. Furthermore, MON-100 was reactive with recombinant 7B2 cleaved from a hybrid protein. In an immunohistochemical study, MON-100 exhibited strong reactivity with the intermediate lobe of the Xenopus pituitary gland, a tissue previously shown to contain 7B2 mRNA. Using MON-100, immunoprecipitation analysis of newly synthesized proteins produced by in vitro incubated Xenopus neurointermediate lobes revealed the biosynthesis of a single protein of Mr 24 kDa, the expected size of the 7B2 protein. It appears, therefore, that the anti-7B2 monoclonal antibody MON-100 can be successfully used for Western blot analysis and immunohistochemical analysis as well as for immunoprecipitation experiments.

Melanin-concentrating hormone system in the brain of the lungfish Protopterus annectens.

The neurochemical anatomy of the lungfish brain is of particular interest, because many features in these animals might be representative of the common ancestor of land vertebrates. In the present study, we have investigated the localization and biochemical characteristics of melanin-concentrating hormone (MCH)-immunoreactive material in the central nervous system of the African lungfish, Protopterus annectens. The most prominent group of MCH-immunoreactive cell bodies was found in the dorsal hypothalamus. Additional groups of MCH-immunoreactive perikarya were detected in the telencephalon within the medial and dorsal pallium, the medial subpallium, and the ventral part of the lateral subpallium. Brightly immunofluorescent nerve fibers were seen in the anterior olfactory nucleus, the ventral part of the medial pallium, the medial subpallium, and the anterior preoptic area. In the diencephalon, the hypothalamus and the medial region of the dorsal thalamus exhibited a dense accumulation of fibers. MCH-immunoreactive fibers were also found in the tectum and the tegmentum of the mesencephalon and within the reticular formation of the rhombencephalon. In the pituitary, several small groups of cells of the intermediate lobe showed a bright fluorescence. Reversed-phase high-performance liquid chromatography (HPLC) analysis of diencephalon and pituitary extracts resolved a major MCH-immunoreactive peak that coeluted with synthetic salmon MCH. The distribution of MCH in the brain of P. annectens suggests that, in lungfishes, this peptide may exert neuromodulator or neurotransmitter functions. The presence of MCH-like immunoreactivity in the intermediate lobe of the pituitary indicates that, in dipnoans, MCH may also act as a typical pituitary hormone.

Development of a novel screening device permitting immunocytochemical screening of numerous culture supernatants during hybridoma production.

A novel screening device is described which permits the simultaneous immunocytochemical processing of several hundreds or even thousands of hybridoma culture supernatants. The core of the screening apparatus is a foam-coated polymer plate that carries a 96-well pattern representing a modification of the actual 96-well template. This modification permits the use of conventional 26 X 76 mm microscopy glass slides. Each of these slides carries 24 carefully arranged histological sections. One 96-well plate is thus screened by mounting four of these slides in the apparatus during the primary antibody (i.e., culture supernatant) incubation stage. At all other stages of the immunocytochemical protocol, the slides are processed in the classical way. The screening apparatus has been used during the production of monoclonal antibodies against chicken pituitary glycoprotein hormones and against bovine neurohypophyseal peptides. In both instances, it proved to be the major contributory factor in the successful production of antibodies.

Application of recombinant DNA technology in epitope mapping and targeting. Development and characterization of a panel of monoclonal antibodies against the 7B2 neuroendocrine protein.

Three mouse monoclonal antibodies (Moabs) have been obtained with specificity for the 7B2 protein, a proposed member of the granin family of neuroendocrine proteins. Bacterially produced hybrid proteins of 7B2 were used as immunogens. The Moabs were designated MON-100, MON-101, and MON-102. Furthermore, we report the construction of 35 deletion mutants of the glutathione S-transferase-7B2 (GST-7B2) fusion-gene using recombinant DNA technology. The hybrid proteins encoded by eleven of these mutants were used in epitope mapping experiments and the results of these studies strongly suggested that recognition of 7B2 by all three Moabs involved the same 16 amino acid region of 7B2 (from amino acid residue 128-135). This was further substantiated by the observation that MON-101 and MON-102 specifically recognized a conjugate between bovine serum albumin and the synthetic peptide Phe-Glu-Pro-Glu-His-Asp-Tyr-Pro-Gly-Leu-Gly-Lys based upon the deduced amino acid sequence of the predicted epitope region in 7B2. In an approach to generate a series of 7B2-specific Moabs targeted against another epitope region in the 7B2 protein, the hybrid protein encoded by deletion mutant pPV32 was used as the immunogen. This protein lacked the epitope region recognized by the first series of Moabs. A second series of three Moabs, designated MON-142, MON-143, and MON-144, was obtained and, in all three cases, the region of 7B2 from amino acid residue 64-94 appeared to be involved in specific recognition by the Moabs. The whole panel of six anti-7B2 antibodies appeared to be useful in immunoprecipitation and Western blot analysis of the 7B2 protein and specifically stained neuroendocrine cells in immunohistochemical experiments. Using a double determinant sandwich enzyme immunoassay, 7B2 protein levels in rat pituitary were determined as 20 ng/mg tissue.

Hypothalamic melanin-concentrating hormone and alpha-neoendorphin-immunoreactive neurons project to the medial part of the rat parabrachial area.

Neurons in the middle and posterior parts of the lateral hypothalamus project to the parabrachial area, and in particular to the gustatory relay-station located in the medial part of this area. In the present study we have examined some of the neuropeptide immunoreactivities of the lateral hypothalamus neurons that project to the gustatory region of the parabrachial area. By coupling retrograde transport and immunohistochemistry, we found that 50-60% of medial parabrachial area-projecting cells located in the juxta-capsular region of the posterior lateral hypothalamus are labeled by rat melanin-concentrating hormone antiserum, while 28% of the retrogradely labeled neurons located in the perifornical lateral hypothalamus are visualized with alpha-neoendorphin antiserum. Moreover, a large number of terminals distributed throughout the parabrachial nucleus are immunoreactive to melanin-concentrating hormone or alpha-neoendorphin antisera. These immunoreactivities are not co-localized within the same lateral hypothalamic neurons. The potential role of these peptidergic projections in the reward mechanisms elicited in the medial parabrachial area and in the control of palatability is discussed.

Production and characterization of specific anti-peptide antiserum against free alpha-subunit of rat pituitary glycoprotein hormones.

To obtain an antibody specific for the alpha-subunit of rat pituitary glycoprotein hormones, we synthesized a peptide corresponding to the sequence 37-53 (ST-7: Phe-Ser-Arg-Ala-Tyr-Pro-Thr-Pro-Ala-Arg-Ser-Lys-Lys-Thr-Met-Leu-Val) of the rat alpha-subunit. The polyclonal antiserum against this peptide was generated in rabbits. This region is hydrophilic and highly conserved among several mammalian species. Noncompetitive binding tests showed that the ST-7 antiserum had specific affinity for the rat free alpha-subunit, but not for rat intact LH, FSH, and TSH. The ST-7 antiserum immunostained two types of cells in the rat anterior pituitary, i.e., gonadotrophs and thyrotrophs. This was also the case in mouse, cattle, sheep, and pig, which have an identical sequence of ST-7 in their alpha-subunit. The pituitary cells of horse (Arg substituted for Lys as residue 48 of the rat alpha-subunit), human, and eel (Leu for Ala at residue 45), chicken (Met for Ala at residue 45), and bullfrog (Tyr for Phe at residue 37 and Met for Ala at residue 45) were not stained with the ST-7 antiserum. This study indicated that the ST-7 antiserum is sequence-specific for the alpha-subunit and is therefore useful for immunohistochemical studies on the secretory pathway of the free alpha-subunit.

Immunoregulation by neuroendocrine factors.

The influence of the pituitary gland and of steroid hormones on the lymphoid system was demonstrated experimentally over half a century ago. Observations indicating the possibility of behavioural modification of immunity were also made at about the same time. Although these initial observations were followed by numerous investigations, the lack of sufficient basic knowledge of the endocrine and immune systems and serious methodological difficulties led to contradictions from which no definite conclusions could be drawn. Thus, the idea of neurohormonal-immune interaction fell gradually into disrepute. The remarkable effect of corticosteroids and their analogues on the immune system was regarded as a pharmacological phenomenon, rather than a physiological mechanism. During the past decade, this area gradually again became one of the forefronts of biomedical investigation and recently a number of volumes have been published on the subject of neurohormonal-immune interactions. Because of space limitations, only a brief overview of the subject can be given below and the reader is referred to the cited literature for detailed information.