Possible Role of Pineal and Extra-Pineal Melatonin in Surveillance, Immunity, and First-Line Defense

Melatonin is a highly conserved molecule found in prokaryotes and eukaryotes that acts as the darkness hormone, translating environmental lighting to the whole body, and as a moderator of innate and acquired defense, migration, and cell proliferation processes. This review evaluates the importance of pineal activity in monitoring PAMPs and DAMPs and in mounting an inflammatory response or innate immune response. Activation of the immune-pineal axis, which coordinates the pro-and anti-inflammatory phases of an innate immune response, is described. PAMPs and DAMPs promote the immediate suppression of melatonin production by the pineal gland, which allows leukocyte migration. Monocyte-derived macrophages, important phagocytes of microbes, and cellular debris produce melatonin locally and thereby initiate the anti-inflammatory phase of the acute inflammatory response. The role of locally produced melatonin in organs that directly contact the external environment, such as the skin and the gastrointestinal and respiratory tracts, is also discussed. In this context, as resident macrophages are self-renewing cells, we explore evidence indicating that, besides avoiding overreaction of the immune system, extra-pineal melatonin has a fundamental role in the homeostasis of organs and tissues.

The interplay between mast cells, pineal gland, and circadian rhythm: Links between histamine, melatonin, and inflammatory mediators

Our daily rhythmicity is controlled by a circadian clock with a specific set of genes located in the suprachiasmatic nucleus in the hypothalamus. Mast cells (MCs) are major effector cells that play a protective role against pathogens and inflammation. MC distribution and activation are associated with the circadian rhythm via two major pathways, IgE/FcεRI- and IL-33/ST2-mediated signaling. Furthermore, there is a robust oscillation between clock genes and MC-specific genes. Melatonin is a hormone derived from the amino acid tryptophan and is produced primarily in the pineal gland near the center of the brain, and histamine is a biologically active amine synthesized from the decarboxylation of the amino acid histidine by the L-histidine decarboxylase enzyme. Melatonin and histamine are previously reported to modulate circadian rhythms by pathways incorporating various modulators in which the nuclear factor-binding near the κ light-chain gene in B cells, NF-κB, is the common key factor. NF-κB interacts with the core clock genes and disrupts the production of pro-inflammatory cytokine mediators such as IL-6, IL-13, and TNF-α. Currently, there has been no study evaluating the interdependence between melatonin and histamine with respect to circadian oscillations in MCs. Accumulating evidence suggests that restoring circadian rhythms in MCs by targeting melatonin and histamine via NF-κB may be promising therapeutic strategy for MC-mediated inflammatory diseases. This review summarizes recent findings for circadian-mediated MC functional roles and activation paradigms, as well as the therapeutic potentials of targeting circadian-mediated melatonin and histamine signaling in MC-dependent inflammatory diseases.

Are cortisol and melatonin involved in the immune modulation by the light environment in pike perch Sander lucioperca?

The pineal gland is the main organ involved in the transduction process converting environmental light information into a melatonin response. Since light environment was described as an important factor that could affect physiology of teleosts, and because melatonin is a crucial hormone regulating numerous physiological processes, we hypothesized that environmental light may act on both stress and circadian axes which in turn could influence the immune status of pike perch. Therefore, we investigated the effects of two light spectra (red and white) and two light intensities (10 and 100 lx) with a constant photoperiod 12L_(8:00-20:00) /12D on pike perch physiological and immune responses. Samples were collected at 04:00 and 16:00 at days 1 and 30 of the experiment. Stress markers, plasma melatonin levels, humoral innate immune markers, and expression of key immune genes in the head kidney were assessed. Light intensity clearly affected pike perch physiology. This included negative growth performances, increase in stress status, decrease in plasma melatonin levels, and immune depression. Light spectrum had only little influences. These results demonstrate that high stress status may have impacted melatonin production and secretion by the pineal organ. The drop in circulating melatonin and the increase in stress status may both be involved in the immune suppression.

The Effect of Light Exposure at Night (LAN) on Carcinogenesis via Decreased Nocturnal Melatonin Synthesis

In mammals, a master clock is located within the suprachiasmatic nucleus (SCN) of the hypothalamus, a region that receives input from the retina that is transmitted by the retinohypothalamic tract. The SCN controls the nocturnal synthesis of melatonin by the pineal gland that can influence the activity of the clock's genes and be involved in the inhibition of cancer development. On the other hand, in the literature, some papers highlight that artificial light exposure at night (LAN)-induced circadian disruptions promote cancer. In the present review, we summarize the potential mechanisms by which LAN-evoked disruption of the nocturnal increase in melatonin synthesis counteracts its preventive action on human cancer development and progression. In detail, we discuss: (i) the Warburg effect related to tumor metabolism modification; (ii) genomic instability associated with L1 activity; and (iii) regulation of immunity, including regulatory T cell (Treg) regulation and activity. A better understanding of these processes could significantly contribute to new treatment and prevention strategies against hormone-related cancer types.

The Immunoendocrine Thymus as a Pacemaker of Lifespan

The thymus develops from an endocrine area of the foregut, and retains the ancient potencies of this region. However, later it is populated by bone marrow originated lymphatic elements and forms a combined organ, which is a central part of the immune system as well as an influential element of the endocrine orchestra. Thymus produces self-hormones (thymulin, thymosin, thymopentin, and thymus humoral factor), which are participating in the regulation of immune cell transformation and selection, and also synthesizes hormones similar to that of the other endocrine glands such as melatonin, neuropeptides, and insulin, which are transported by the immune cells to the sites of requests (packed transport). Thymic (epithelial and immune) cells also have receptors for hormones which regulate them. This combined organ, which is continuously changing from birth to senescence seems to be a pacemaker of life. This function is basically regulated by the selection of self-responsive thymocytes as their complete destruction helps the development (up to puberty) and their gradual release in case of weakened control (after puberty) causes the erosion of cells and intercellular material, named aging. This means that during aging, self-destructive and non-protective immune activities are manifested under the guidance of the involuting thymus, causing the continuous irritation of cells and organs. Possibly the pineal body is the main regulator of the pacemaker, the neonatal removal of which results in atrophy of thymus and wasting disease and its later corrosion causes the insufficiency of thymus. The co-involution of pineal and thymus could determine the aging and the time of death without external intervention; however, external factors can negatively influence both of them.

[THE CHANGES OF THE INTERRELATIONS OF THE PINEAL GLAND AND THE ORGANS OF THE IMMUNE SYSTEM IN RATS IN RESPONSE TO MELATONIN ADMINISTRATION IN LIGHT REGIME DISTURBANCES]

In this work the correlation analysis was applied to detect the integrated response of the pineal gland (PG) and immunocompetent organs of male Wistar rats in response to administration of melatonin (MT) in light regime disturbances. Animals were kept for 14 days under natural or continuous light (CL). Then for 7 days they received the injections of either 0.9% solution of sodium chloride or MT, after which the rats were decapitated and the mass of their body, PG, thymus and spleen was determined. The lymphocyte subpopulations of the thymus and spleen were studied by flow cytometry. The amount of lipofuscin in PG was assessed by the intensity of autofluorescence in organ frozen sections in 560-600 nm wavelength range. It was found that under the influence of MT, the number of intraorgan correlations in the immune system increased, regardless of the light regime. In animals on CL treated with MT, the number of interorgan connections was reduced, while negative correlations appeared between PG lipofuscin content and cellular composition of the spleen. The synchronizing and adaptogenic effects of MT were most pronounced under conditions of CL.

[Interrelations of pineal gland morpho-functional indices and immune system organs in rats exposed to natural illumination regime and continuous illumination]

The objective of this investigation was to determine the complex response of the pineal gland (PG) and of the organs of the immune system in Wistar rats in response to a violation of the illumination regime in the experiment. Animals were kept under natural light regime and continuous illumination for 14 days. After that rats were sacrificed and the mass of the body, PG, gonads, thymus and spleen was measured. Thymus and spleen cell subpopulations were determined by flow cytometry. The lipofuscin content in PG was determined by measuring an autofluorescence intensity in frozen tissue sections in the wavelength range of 505-545 nm using a confocal laser scanning microscope LSM 510 META (Carl Zeiss). The correlation analysis showed an increase in the amount and the change of sign and direction of relations between the indices of the state of PG and the immune system. This indicates the up-regulation of the intensity of inter-system relationships and the change of migration and differentiation vector of immunocompetent cells.

The pineal regulation of the immune system: 40 years since the discovery

The first observation on the relationship between the pineal gland and the immune system was done by the author of this paper in the late sixties and early seventies of the last century. After neonatal pinealectomy the thymus has been destroyed and wasting disease developed. Since that time a flood of experiments justified the observation and pointed to the prominent role of pineal in the regulation of the immune system. Melatonin, the hormone of the pineal gland stimulates immune processes acting to the immune cells' cytokine production, the haemopoiesis, and immune cell-target cell interactions. Melatonin receptors have been demonstrated and their localization and function were justified. Melatonin production by and melatonin receptors on (and in) the immune cells was proved. Melatonin agonists have been synthesized and the use of melatonin as adjuvant in the therapy of diseases connected to the immune system (cancers included) has been started. The paper summarizes the most important studies and discusses the interrelations of the data. The discussion points to the possibility of packed transport of the pineal hormone by the immune cells and to the adventages of local regulation by this transport.

The concept of the immune-pineal axis tested in patients undergoing an abdominal hysterectomy

OBJECTIVE

Activation of the immune-pineal axis induces a transient reduction in nocturnal melatonin in the plasma during the proinflammatory phase of an innate immune response to allow the proper migration of leukocytes to the lesion site. This transient reduction should be regulated by inflammatory mediators, which are responsible for the fine-tuning of the process. In the present study, we measured the pre- and postoperative serum concentrations of melatonin, tumor necrosis factor (TNF) and cortisol in women who underwent an elective hysterectomy and correlated the variation in melatonin with postoperative pain.

METHODS

We evaluated 12 women who had an abdominal hysterectomy. Blood was collected at 10.00 and 22.00 h 1 week and 1 day before the surgery, on the 1st and 2nd days after the surgery and at 22.00 h on the day of the surgery.

RESULTS

On the night after the surgery, there was no melatonin detected at 22.00 h. High TNF levels were accompanied by a lower nocturnal melatonin output, higher postoperative pain according to a visual analog scale and the request of higher doses of analgesics. In addition, low cortisol levels were accompanied by a lower nocturnal melatonin output.

CONCLUSION

Our results confirm that the same antagonistic pattern between TNF and glucocorticoids observed in cultured pineal glands also occurs in humans. This integrative pattern suggests that the cross talk between the immune and endocrine system orchestrates longitudinal changes in pineal activity, reinforcing the hypothesis of an immune-pineal axis.

Glia-pinealocyte network: the paracrine modulation of melatonin synthesis by tumor necrosis factor (TNF)

The pineal gland, a circumventricular organ, plays an integrative role in defense responses. The injury-induced suppression of the pineal gland hormone, melatonin, which is triggered by darkness, allows the mounting of innate immune responses. We have previously shown that cultured pineal glands, which express toll-like receptor 4 (TLR4) and tumor necrosis factor receptor 1 (TNFR1), produce TNF when challenged with lipopolysaccharide (LPS). Here our aim was to evaluate which cells present in the pineal gland, astrocytes, microglia or pinealocytes produced TNF, in order to understand the interaction between pineal activity, melatonin production and immune function. Cultured pineal glands or pinealocytes were stimulated with LPS. TNF content was measured using an enzyme-linked immunosorbent assay. TLR4 and TNFR1 expression were analyzed by confocal microscopy. Microglial morphology was analyzed by immunohistochemistry. In the present study, we show that although the main cell types of the pineal gland (pinealocytes, astrocytes and microglia) express TLR4, the production of TNF induced by LPS is mediated by microglia. This effect is due to activation of the nuclear factor kappa B (NF-kB) pathway. In addition, we observed that LPS activates microglia and modulates the expression of TNFR1 in pinealocytes. As TNF has been shown to amplify and prolong inflammatory responses, its production by pineal microglia suggests a glia-pinealocyte network that regulates melatonin output. The current study demonstrates the molecular and cellular basis for understanding how melatonin synthesis is regulated during an innate immune response, thus our results reinforce the role of the pineal gland as sensor of immune status.

Psychoneuroendocrine modulation of regulatory T lymphocyte system: in vivo and in vitro effects of the pineal immunomodulating hormone melatonin

BACKGROUND

At present, it is known that cancer-related immunosuppression would mainly depend on an immunosuppressive action mediated by a subtype of CD4+ lymphocytes, the so-called regulatory T lymphocytes (T-reg), which are identified as CD4+CD25+ cells. Moreover, it has been shown that anticancer immunity is under psychoneuroendocrine regulation, mainly mediated by the pineal hormone melatonin (MLT). This study was performed to investigate the in vivo and in vitro effects of MLT on T-reg generation.

MATERIALS AND METHODS

We evaluated the in vivo effects of MLT (20 mg/daily orally in the evening) in 20 patients with untreatable metastatic solid tumor and the in vitro effects of MLT incubation (at 10 and 100 pg/ml) of pure lymphocyte cultures on T-reg cell count.

RESULTS

MLT induced a statistically significant decline in mean T-reg cell numbers in patients who achieved disease control, whereas no effect was seen in those who had progressed. In contrast, no in vitro effect of MLT incubation was apparent.

CONCLUSION

This preliminary study would suggest that MLT may exert in vivo an inhibitory action on T-reg cell generation in cancer patients which is associated with a control of the neoplastic progression, whereas no direct effect was seen in vitro on lymphocyte differentiation. This finding would suggest that MLT may counteract T-reg cell generation in vivo by inhibiting macrophage activity which is involved in stimulating T-reg cell production.

TLR4 and CD14 receptors expressed in rat pineal gland trigger NFKB pathway

Nuclear factor-kappa B (NFKB), a pivotal player in inflammatory responses, is constitutively expressed in the pineal gland. Corticosterone inhibits pineal NFKB leading to an enhancement of melatonin production, while tumor necrosis factor (TNF) leads to inhibition of Aa-nat transcription and the production of N-acetylserotonin in cultured glands. The reduction in nocturnal melatonin surge favors the mounting of the inflammatory response. Despite these data, there is no clear evidence of the ability of the pineal gland to recognize molecules that signal infection. This study investigated whether the rat pineal gland expresses receptors for lipopolysaccharide (LPS), the endotoxin from the membranes of Gram-negative bacteria, and to establish the mechanism of action of LPS. Here, we show that pineal glands possess both CD14 and toll-like receptor 4 (TLR4), membrane proteins that bind LPS and trigger the NFKB pathway. LPS induced the nuclear translocation of p50/p50 and p50/RELA dimers and the synthesis of TNF. The maximal expression of TNF in cultured glands coincides with an increase in the expression of TNF receptor 1 (TNFR1) in isolated pinealocytes. In addition, LPS inhibited the synthesis of N-acetylserotonin and melatonin. Therefore, the pineal gland transduces Gram-negative endotoxin stimulation by producing TNF and inhibiting melatonin synthesis. Here, we provide evidence to reinforce the idea of an immune-pineal axis, showing that the pineal gland is a constitutive player in the innate immune response.

Association of mast cells with calcification in the human pineal gland

Increased pineal calcifications and decreased pineal melatonin biosynthesis, both age related, support the notion of a pineal bio-organic timing mechanism. The role of calcification in the pathogenesis of pineal gland dysfunction remains unknown but the available data document that calcification is an organized, regulated process, rather than a passive aging phenomenon. The cellular biology and micro-environmental conditions required for calcification remain poorly understood but most studies have demonstrated evidence that mast cells are strongly implicated in this process. The aim of the present study was to examine the phenotype of mast cells associated with early stages and with the progressive development of calcification in the human pineal gland. The study was performed on pineal samples of 170 fetuses and children whose brains were autopsied and diagnosed during 1998-2002. The representative cerebral and pineal specimens were stained with haematoxylin and eosin or the von Kossa staining technique and for the distribution of mast cell tryptase, mast cell chymase, histamine H4 receptor and vascular network using biotinylated Ulex europaeus agglutinin. Tryptase mast cells were found in all stages of pineal gland development independently of the presence of local tissue lesions. All of them were always localized in the close vicinity of the blood vessels and expressed immunoreactivity to histamine H4 receptor antibody. Immunolocalization of mast cells by chymase antibody (and following dual immunostaining with both chymase and tryptase antibodies) demonstrated that these cells were few in number and were located in the subcapsular region of the gland. In our study, all functional mast cells that underwent activation and were co-localized with deposits of calcium did not contain chymase. All of them were stained with tryptase and represent the MC-T phenotype. Tryptase mast cells and extracellular tryptase were often associated with areas of early and more advanced stages of calcification. Our results lead to the conclusion that the tryptase mast cells play a major role in the pineal calcification process as sites where this process starts and as a source of production of numerous biologically active substances including tryptase that participate in calcification.

In vivo actions of melatonin on the innate immune parameters in the teleost fish gilthead seabream

Melatonin, a molecule produced in the pineal gland and retina of vertebrates, plays a major role in day-night circadian rhythms and other physiological processes, including the immune responses. Because little is known in this respect in fish, we have evaluated the in vivo role of melatonin in the main innate immune activities and the expression of immune-relevant genes in a teleost fish, the gilthead seabream (Sparus aurata L.). An intraperitoneal injection of 1 or 10 mg melatonin/kg of body weight produced a dose-time dependent increase in circulating melatonin serum levels. Several innate immune responses such as peroxidase, phagocytic, reactive oxygen intermediates and cell-mediated cytotoxic activities were significantly enhanced by the administration of melatonin at different sampling times. The expression of immune-relevant genes such as interleukin-1beta, major histocompatibility complex, virus-related response (interferon-regulatory factor-1 and Mx) and lymphocyte markers (immunoglobulin M and T-cell receptor for B and T lymphocytes, respectively), as analysed by semi-quantitative reverse transcription-polymerase chain reaction, was up-regulated in the head-kidney of melatonin-injected fish 1 and 3 days postinjection and decreased after 7 days. These data, together with our previous observations describing how photoperiod and in vitro melatonin treatment may affect seabream and sea bass immunology, confirm melatonin as a regulator of fish immunology. However, further studies are still needed to reveal the mechanisms underlying the direct or indirect interactions of melatonin with the fish immune system.

Pineal melatonin and the innate immune response: the TNF-alpha increase after cesarean section suppresses nocturnal melatonin production

The nocturnal surge of melatonin is the endocrine expression of the circadian system and is essential for organizing the timing of various endogenous processes. Previous works suggest that, in the beginning of a defense response, the increase in circulating tumor necrosis factor-alpha (TNF-alpha) leads to a transient block of nocturnal melatonin production and promotes a disruption of internal time organization. In the present paper, the concentration of melatonin and cytokines [TNF-alpha, interferon-gamma (IFN-gamma), interleukin (IL)-2, IL-4, IL-5, IL-10, IL-12] in the colostrum (postdelivery day 3) and in the milk (postdelivery days 10, 15, 20 and 30) obtained at midday and midnight from mothers who gave birth by vaginal or cesarean section were compared. The nocturnal melatonin surge observed 3 days after vaginal delivery was absent after cesarean section. IL-12 presented no daily variation in either case, while daily variations in IFN-gamma, IL-10, IL-4 and IL-5 were observed after vaginal delivery and cesarean section. On the other hand, the increase in TNF-alpha after cesarean section resulted in suppression of the nocturnal melatonin surge. Daily variation of IL-2 was only observed after recovery of the nocturnal melatonin surge, 30 days after cesarean section. The present paper supports the hypothesis of a cross-talk between the pineal gland and the immune system, which could represent a putative immune-pineal axis.

Neural adrenergic/cyclic AMP regulation of the immunoglobulin E receptor alpha-subunit expression in the mammalian pinealocyte: a neuroendocrine/immune response link?

The high affinity immunoglobulin E receptor (FcepsilonRI) complex is dedicated to immunoglobulin E-mediated allergic responses. Expression of the FcepsilonRI receptor is thought to be relatively stable and limited to mast cells, basophils, eosinophils, monocytes, Langerhans cells, platelets, and neutrophils. We now report that the FcepsilonRIalpha and FcepsilonRIgamma polypeptides are expressed in the pinealocyte, the melatonin-secreting cell of the pineal gland. Moreover, Fcer1a mRNA levels increased approximately 100-fold at night to levels that were higher than in other tissues examined. Pineal FcepsilonRIalpha protein also increased markedly at night from nearly undetectable daytime levels. Our studies indicate that pineal Fcer1a mRNA levels are controlled by a well described neural pathway that controls pineal function. This pathway includes the master circadian oscillator in the suprachiasmatic nucleus and passes through central and peripheral structures. The circadian expression of FcepsilonRIalpha in the pineal gland is driven by this neural circuit via an adrenergic/cyclic AMP mechanism. Pineal FcepsilonRIalpha and FcepsilonRIgamma may represent a previously unrealized molecular link between the neuroendocrine and immune systems.

The immune-pineal axis: a shuttle between endocrine and paracrine melatonin sources

The time course of the innate immunological response involves a pro-inflammatory phase followed by an anti-inflammatory phase. Pro-inflammatory responses serve as a defense against several stressor conditions, and sequential processes that shut down these responses are necessary to avoid exacerbation or the development of chronic diseases. In the present review, we put together recent data that show that the pineal gland is a player in bidirectional control of the inflammatory response. Healthy organisms stay in standby mode, ready to react. The nocturnal melatonin surge impairs the rolling and adherence of leukocytes to endothelial layers, limiting cell migration, and stimulates nocturnal production of IL-2 by T helper lymphocytes, exerting an immunostimulatory effect. Otherwise, the release of TNF-alpha from activated macrophages suppresses the nocturnal melatonin surge, allowing a full cell migration and inhibiting IL-2 production. In sequence, activated mononuclear and polymorphonuclear cells produce melatonin in a paracrine manner at the site of injury, which scavenges free radicals and collaborates to resolve the inflammatory response. The sequential diminution of TNF-alpha production is followed by the recovery of the nocturnal melatonin surge and IL-2 production. In summary, the immune-pineal axis, implicated in the sequential involvement of the melatonin produced by the pineal gland and immune-competent cells, is an integral participant of the innate immune response.

[Immunotoxicity of metals and protective function of pineal factors]

Analysis of the literature data shows that different metals has immunotoxical properties. Biological active compounds of the pineal gland and especially its main hormone, melatonin decreased of toxic shifts through normalization of immune state.

Effect of TNF-alpha on the melatonin synthetic pathway in the rat pineal gland: basis for a 'feedback' of the immune response on circadian timing

A retino-hypothalamic-sympathetic pathway drives the nocturnal surge of pineal melatonin production that determines the synchronization of pineal function with the environmental light/dark cycle. In many studies, melatonin has been implicated in the modulation of the inflammatory response. However, scant information on the feedback action of molecules present in the blood on the pineal gland during the time course of an inflammatory response is available. Here we analyzed the effect of tumor necrosis factor-alpha (TNF-alpha) and corticosterone on the transcription of the Aa-nat, hiomt and 14-3-3 protein genes in denervated pineal glands of rats stimulated for 5 hr with norepinephrine, using real-time reverse transcription-polymerase chain reaction. The transcription of Aa-nat, a gene encoding the key enzyme in melatonin biosynthesis, together with the synthesis of the melatonin precursor N-acetylserotonin, was inhibited by TNF-alpha. This inhibition was transient, and a preincubation of TNF-alpha for more than 24 hr had no detectable effect. In fact, a protein(s) transcribed, later on, as shown by cycloheximide, was responsible for the reversal of the inhibition of Aa-nat transcription. In addition, corticosterone induced a potentiation of norepinephrine-induced Aa-nat transcription even after 48 hr of incubation. These data support the hypothesis that the nocturnal surge in melatonin is impaired at the beginning of an inflammatory response and restored either during the shutdown of an acute response or in a chronic inflammatory pathology. Here, we introduce a new molecular pathway involved in the feedback of an inflammatory response on pineal activity, and provide a molecular basis for understanding the expression of circadian timing in injured organisms.

A new procedure for experimental autoimmune uveitis with small uveitogenic peptides

PURPOSE

Demonstration of experimental autoimmune uveitis (EAU) with extremely small, fragmented peptides (12-30 amino acid residues) of interphotoreceptor retinoid-binding protein (IRPB).

METHOD

Very small fragmented peptides (no. 854, 888, 907, and 1057) were conjugated to heat-killed Group A Streptococcus cells and administered as a single intravenous injection to Lewis rats. A non-uveitogenic peptide 950 was also conjugated to heat-killed Streptococcus and administered. Administration of a mixture of small peptides and Streptococcus was a control for the peptides conjugated with Streptococcus.

RESULTS

The uveitogenic peptide/Streptococcus conjugates produced uveitis inflammatory responses in the uvea, retina and pineal gland. Administration of mixtures of small peptides and Streptococcus cells, and a non-uveitogenic peptide 950 conjugated with Streptococcus did not produce autoimmune uveitis.

CONCLUSIONS

Since mixtures of small uveitogenic peptides and Streptococcal cells did not develop autoimmune uveitis, conjugated Streptococcal cells provided a vehicle for macrophage phagocytosos of very small uveitogenic IRBP peptides. Subsequent antigen presentation from macrophages to lymphocytes developed autoimmune uveitis. Peptide 888, one of four IRBP peptides that encompass the major uveitogenic domain, proved to be the most effective in development of uveitis.

Characterization of lymphocyte subsets over a 24-hour period in Pineal-Associated Lymphoid Tissue (PALT) in the chicken

BACKGROUND

Homeostatic trafficking of lymphocytes in the brain has important relevance to the understanding of CNS disease processes. The pineal gland of the chicken contains large accumulations of lymphocytes that suggest an important role related to homeostatic circadian neuro-immune interactions. The purpose of this initial study was to characterize the lymphocyte subsets in the pineal gland and quantitate the distribution and frequency of lymphocyte phenotypes at two time points over the 24-hour light:dark cycle.

RESULTS

PALT comprised approximately 10% of the total pineal area. Image analysis of immunocytochemically stained sections showed that the majority of lymphocytes were CD3+ (80%) with the remaining 20% comprising B-cells and monocytes (Bu-1+), which tended to distribute along the periphery of the PALT. T-cell subsets in PALT included CD4+ (75-80%), CD8+ (20-25%), TCRalphabeta/Vbeta1+ (60%), and TCRgammadelta+ (15%). All of the T-cell phenotypes were commonly found within the interfollicular septa and follicles of the pineal gland. However, the ratios of CD8+/CD4+ and TCRgammadelta+/TCRalphabeta/Vbeta1+ within the pineal tissue were each 1:1, in contrast to the PALT where the ratios of CD8+/CD4+ and TCRgammadelta+/TCRalphabeta/Vbeta1+ each approximated 1:4. Bu-1+ cells were only rarely seen in the pineal interstitial spaces, but ramified Bu-1+ microglia/macrophages were common in the pineal follicles. Effects of the 24-h light:dark cycle on these lymphocyte-pineal interactions were suggested by an increase in the area of PALT, a decline in the density of TCRalphabeta/Vbeta1+ cells, and a decline in the area density of Bu-1+ microglia at the light:dark interphase (1900 h) compared to the dark:light interphase (0700 h).

CONCLUSION

The degree of lymphocyte infiltration in the pineal suggests novel mechanisms of neuro-immune interactions in this part of the brain. Our results further suggest that these interactions have a temporal component related to the 24-hour light:dark cycle and that CD8+ and TCRgammadelta+ T-cells are preferentially recruited to the pineal follicles. Pineal microglia/macrophages were common and represent an important candidate for mediating these lymphocyte-pineal interactions via secretion of cytokines and chemokines.

Antigen-induced changes in the endocrine function of the thymus in CBA mice during aging: role of peptide factors released by the pineal gland

The titer of thymic serum factor was measured in adult and old CBA females 15, 30, and 60 min, 24, 48, 72, and 96 h after injection of 3% suspension of sheep erythrocytes and changes of this parameter under the effect of epithalamin were studied in old immunized mice. The titer of thymic serum factor increased appreciably in adult mice virtually at all periods of the study after immunization (a drop was observed only 72 h after immunization). In old mice the titer of thymic serum factor virtually did not change after injection of sheep erythrocytes, while immunization of old mice preinjected with epithalamin significantly increased this parameter. Not only the values, but their dynamics in old mice injected with epithalamin corresponded to those in immunized adult animals.

Time course and role of the pineal gland in photoperiod control of innate immune cell functions in male Siberian hamsters

The time course of select phagocyte and natural killer activities to short days was determined. In advance of testes regression, circulating granulocyte and monocyte cell numbers in hamsters decreased while lymphocyte numbers increased; phagocytosis and oxidative burst activity also decreased. To determine whether the pineal gland influences these innate immune cell functions, hamsters were exposed to constant light. Photoperiod control of testes weight and basal oxidative burst activity was abolished by treatment with constant light; other phagocyte activities and leukocyte proportions in circulation were not affected. The findings suggest that photoperiod and pineal gland function may regulate certain innate immune activities.

Demonstration of PACAP-immunoreactive intrapineal nerve fibers in the golden hamster (Mesocricetus auratus) originating from the trigeminal ganglion

By using immunohistochemistry, a network of nerve fibers containing pituitary adenylate-cyclase activating polypeptide (PACAP) was demonstrated in the pineal gland of the golden hamster, a photoperiodic species often used in pineal and circadian rhythm research. The nerve fibers are present in the capsule from where they permeate into the pineal perivascular spaces and parenchyma. Immuno-electron microscopy showed the PACAPergic nerve terminals, with clear transmitter vesicles, to terminate in the interstitial spaces between the pinealocytes or in the perivascular spaces. Some of the PACAPergic nerve terminals made synapse-like contacts with the pinealocytes. The origin of the PACAP-containing nerve fibers innervating the pineal gland of the hamster was investigated by combined retrograde tracing with fluorogold and immunohistochemistry for PACAP. A 2% fluorogold solution was injected iontophoretically into the superficial pineal gland and the animals were allowed to survive for 1 wk. After perfusion fixation of the rats, the location of the tracer was investigated in the brain, the parasympathetic sphenopalatine, and otic ganglia, as well as in the sensory trigeminal ganglia. The tracer was found in perikarya of all the investigated ganglia. However, co-localization with PACAP was found only in the trigeminal ganglion.

[Age-related characteristics of the melatonin-producing epiphyseal function in CBA mice immunized by T-dependent antigen]

It was investigated both melatonin blood level in the adult and old CBA-mice after immunization by sheep erythrocytes and the link between thymus and adrenal glands function in the old immunizated mice with high melatonin content in the pineal gland. It has been revealed that in the adult mice blood melatonin level was influenced by the phase changes in dynamic of immunization, namely raised significantly in 20 min with following suppression after 3 hrs and rehabilitation up to normal in 4 days. In the old mice fluctuations of melatonin level were impaired and characterized by gradually decrease in dynamics of immunization. The increase of melatonin content in pineal gland by administration of epithalamine improved the dynamics of fluctuations of thymic hormone and corticosterone level in the immunizated old mice.

Neuropeptide Y (NPY) and C-flanking peptide of NPY in the pineal gland of normal and ganglionectomized sheep

The present immunohistochemical study describes the presence and distribution of nerve fibers containing neuropeptide Y (NPY), and C-Flanking Peptide Of NPY (CPON) in the pineal gland of the sheep. Nerve fibers were detected by using a series of antisera directed against NPY or against CPON. Many positive immunoreactive nerve fibers were identified in the pial capsule of the pineal, in connective septae and in the parenchyma between pinealocytes. The intraparenchymal fibers were particularly evident and created an extensive network throughout the gland. Nerve fibers immunoreactive for all the peptides were also observed in the posterior commissure and in the stria medullaris thalami. No NPY- or CPON-positive neurons were found in the pineal gland. In order to study the site of origin of NPY- and CPON-immunoreactive nerve fibers, the superior cervical ganglia were bilaterally removed in a series of animals. Sympathetic denervation was checked by using an antiserum against tyrosine hydroxylase (TH). Nearly all TH-immunoreactive elements disappeared in the pineal glands of animals sacrificed 15 days after surgery. Also the density of NPY- and CPON-immunoreactive nerve fibers decreased in the animals after the ganglionectomy. However, a number of nerve fibers still remained in the gland. These data indicate that some NPY- and CPON-immunoreactive nerve fibers of the sheep pineal gland derive from an extrasympathetic origin. The very dense innervation of the sheep pineal gland with nerve fibers containing NPY and CPON strongly indicates a functional role for this family of peptides in the pineal gland of this species.

The influence of immunomodulation on psycho-neuroimmunological functions in benign multiple sclerosis

OBJECTIVES

In multiple sclerosis (MS), several neuroimmunomodulatory effectors are known, including melatonin. They are able to influence disease-related neurophysiogical changes (disability or impaired vision) as well as neuropsychological performance (e.g. cognition and depression). In this study we assessed the relationship between immunomodulation on psycho-neuroimmunological functions in benign multiple sclerosis.

METHODS

We evaluated 26 young female patients with benign MS treated with/without immunomodulating therapies with regard to their physical disabilities (Expanded Disability Status Scale, EDSS), their visually evoked potentials (VEP), their plasma melatonin concentrations as well as their performance regarding emotional and cognitive tests and compared them with healthy matched controls.

RESULTS

Patients with MS showed deficits in cognitive and emotional functions compared to healthy controls, which were in accordance with their increase in EDSS over time. However, in contrast to untreated patients, patients receiving immunotherapy showed significantly increased dysfunction with respect to actual mood (p = 0.02) and a tendency to increased depression scores (p = 0.072). However, neither treatment subgroup had cognitive deficits. In untreated patients, melatonin levels correlated with reduced scores in the cognitive tests (p = 0.045) but not with depression or VEP latencies. Patients with long-standing MS (>10 years) showed a significant correlation (p = 0.01) to their increased depression scores and their melatonin levels, but no correlation with VEP or cognitive dysfunction, compared to patients with shorter disease duration (< or =10 years).

CONCLUSION

These results indicate that in MS all aspects of the psycho-neuroimmunological network can be affected. Despite the potential influence of immunomodulation on depression, no connection with melatonin representing the retinohypothalamic tract/pineal gland circuits could be detected. However, visual perception as well as visuoconstructive abilities were affected in MS patients. Neuropsychological tests in MS should concentrate on cognitive variables, which reflect the clinical status more accurately and may be used to monitor disease-modifying therapies.

Regional heterogeneity in immunoreactive macrophages/microglia in the rat pineal gland

Using specific macrophage antibodies (OX-42, OX-6, ED-1 and ED-2), this study examined the distribution of macrophages/microglia in the pineal gland of adult rats. Except for ED-2, all antibodies labeled distinct subpopulations of macrophages/microglia in the gland; ED-2 labeling was hardly detectable. The quantitative study showed that the pineal macrophages/microglia (PMM) expressing complement type 3 receptors (OX-42) were more numerous than those expressing the major histocompatibility complex class II antigen (OX-6) or unknown cytoplasmic/lysosomal antigens (ED-1). The PMM were ubiquitous, especially the OX-42 labeled cells which were distributed from the dorsal to the ventral aspect of the gland. The macrophages/microglia labeled with OX-6 or ED-1 were localized mainly in the intermediate portion of the pineal gland. Immunolabeled cells were sparsely distributed in the distal portion of the pineal gland. A notable feature was that the OX-6 labeled macrophages/microglia showed a proximal-distal gradient in cell density. Another interesting feature was the occurrence of prominent cell aggregations around the larger blood vessels. These cells were mostly round and exhibited different immunoreactivity. Confocal microscopic study with triple immunolabeling further revealed that individual PMM cell possessed two or more different antigens (ED-1+/OX-6+, OX-42+/OX-6+ or OX-42+/ED-1+). Remarkably, a large population co-expressed ED-1+/OX-6+/OX-42+. The present results show that the expression of immunoreactive molecules in PMM varies in topographical distribution of the cells. It is suggested that this may be linked to their immunoregulatory functions in the gland.

Immunohistochemical localization of human pineal tissue antigens in normal retina and retinoblastomas

The normal human retina and retinoblastomas were examined immunohistochemically to assess the localization of pineal antigens in the retina and the oncogenesis and differentiation of retinoblastoma. In the present study, 41 eyes excised from children (aged 4 months to 7 years, all unilateral occurrence) diagnosed to have retinoblastoma and 4 eyes with normal retinas, were used. Retinoblastomas were histopathologically classified into well-differentiated, moderately-differentiated, and poorly-differentiated types. The antibodies used were 9 monoclonal antibodies to human pineal antigens and 6 antibodies to neural tissues. In the normal retina, staining patterns characteristic of retinal cell layers were observed with PP1, PP3, PP5, PP6, PI1, and PI2 antibodies. In retinoblastomas, PP5 antibody, which reacts with horizontal cells and ganglion cells, and PP6 antibody, which reacts with part of the bipolar cells in the inner nuclear layer, showed intense staining in well-differentiated retinoblastomas, but the intensity of staining and the positivity decreased with the degree of dedifferentiation. Antigens recognized by PP3 and PP4 antibodies were positive in all retinoblanstomas. Reactions to GFAP antibody and antibodies that recognize Müller cells were negative. Retinoblanstomas may express markers of not only photoreceptor cells but also other retinal nuclear cells. These results suggest that the retinoblastoma might be developed from visual stem cells, which are common progenitor cells of photoreceptor cells, intermediate neurons, and ganglion cells.

Bidirectional communication between the pineal gland and the immune system

The pineal gland is a vertebrate neuroendocrine organ converting environmental photoperiodic information into a biochemical message (melatonin) that subsequently regulates the activity of numerous target tissues after its release into the bloodstream. A phylogenetically conserved feature is increased melatonin synthesis during darkness, even though there are differences between mammals and birds in the regulation of rhythmic pinealocyte function. Membrane-bound melatonin receptors are found in many peripheral organs, including lymphoid glands and immune cells, from which melatonin receptor genes have been characterized and cloned. The expression of melatonin receptor genes within the immune system shows species and organ specificity. The pineal gland, via the rhythmical synthesis and release of melatonin, influences the development and function of the immune system, although the postreceptor signal transduction system is poorly understood. Circulating messages produced by activated immune cells are reciprocally perceived by the pineal gland and provide feedback for the regulation of pineal function. The pineal gland and the immune system are, therefore, reciprocally linked by bidirectional communication.

Differential labeling of the pinealocytes and pineal interstitial cells by a series of monoclonal antibodies to human pineal body

Ten hybridomas producing monoclonal antibodies against pineal antigens were established by hybridizing mouse myeloma cells with spleen cells from BALB/c mice immunized with human pineal body homogenate. Seven antibodies immunohistochemically reacted with the pinealocytes and three reacted with the pineal interstitial cells. According to the antibodies applied, the pinealocytes were immunostained in a variable manner; granularly with PP1, PP4 and PP6 antibodies, diffusely with PP2 and PP5, membraneously with PP3, and apically with PP7. The PI1 and P12 antibodies immunolabeled most of the interstitial cells, but PX1 immunolabeled only a small population of these cells. An immunoblotting study indicated that single or multiple polypeptides of the pineal homogenate constituted the antigen epitopes for these antibodies. Most antibodies also immunoreacted with several cell types of the extra-pineal tissues, thus these antibodies are not specific to the human pineal body. This series of monoclonal antibodies should be available for immunohistochemical studies involving the normal and pathological human pineal body.

Melatonin-immune system relationships

In this paper we review the historical milestones that first highlighted the existence of a relationship between melatonin and the immune system and we summarize data from experiments which correlate the rhythmic production of melatonin with the rhythmic activity of the immune system. The effects of pinealectomy and in vivo administration of melatonin on a variety of immune parameters, including specific and non-specific immunity are considered and we also present contradictory data concerning the effect of melatonin in cultured immunocompetent cells and a possible scheme of how melatonin regulates the production of a number of cytokines. Finally, the mechanism of action of melatonin in the immune system is discussed. Many data suggest the existence of both nuclear and membrane receptors for melatonin in the immune system. Both of these appear to be clearly identified but their specific physiological role is still under discussion. In summary, although there is overwhelming information demonstrating the immunoenhancing properties of melatonin, many questions related to the cytokines involved and the mechanisms of action of the indoleamine require answers.

Uveitopathogenic sites in recoverin

PURPOSE

This study was carried out in order to determine the most potent and novel uveitopathogenic sites of recoverin using synthetic peptides.

METHODS

Several synthetic peptides containing the recoverin sequence plus adjuvants were injected into Lewis rats, and the uveitopathogenic sequence was defined, clinically, histologically, and immunologically.

RESULTS

Peptides containing of amino acids 57-85 and 136-167 induced severe EAU, and the lowest doses to induce EAU were 20 microg and 10 microg, respectively. Lymphocyte proliferative reactions were also positive for peptides 57-85 and 136-167. The core sequences within the uveitopathogenic site were 65-79 and 153-164. Peptides of amino acids 65-79 within 57-85 and 149-167 within 136-167 were the smallest in the recoverin sequence, respectively, that could induce severe EAU.

CONCLUSION

We found recoverin has some novel potent uveitopathogenic sites, 149-167. These findings of the uveitopathogenic sites in recoverin may lead to improved understanding of the pathogenesis of uveitis and the means to design specific treatment.

Effect of pinealectomy on immune parameters in rats with Staphylococcus aureus infection

It is generally accepted that the pineal gland is a neuroendocrine organ. Several recent experiments have shown that the pineal gland has functional and anatomical connections, particularly with the immune system, and therefore the gland is now recognized as an important immunoneuroendocrine organ in both man and animals. The present study investigates the effect of pinealectomy on some immune parameters, including hematological alterations, and the response of the brain tissue against infection caused by Staphylococcus aureus. Experiments were performed on two different age groups of rats (neonatal and young). The results showed a significant reduction of the plasma zinc level in the third week following pinealectomy, impairment of the hematological parameters including lymphocyte, erythrocyte, and leucocyte, and the deficiency of the brain response to the infective agent, particularly in pinealectomized neonatal rats. In view of these data and as described previously, the pineal gland has a main regulatory function in immune physiology, but our study indicates that only neonatal immune functions are significantly affected by pinealectomy.

The effects of melatonin on humoral immune responses of young and aged rats

The pineal gland with its effects on immune system and free radicals may have a role on aging process. In this study, we investigated the effects of melatonin (10 mg/kg/d, s.c. for 7 days), the main secretion of the pineal gland, on the humoral immune responses of aged and young male Wistar rats. Eighteen aged (28 months old; 6 in control group and 12 in melatonin group) and 25 young (9 months old; 10 in control group and 15 in melatonin group) rats were given 4 x 10(8) sheep erythrocytes i.p. in order to evoke humoral immune responses. After a booster injection at the end of a period of three-weeks following the last melatonin injection, IgM and IgG1 levels were measured. Melatonin was found to increase IgG1 and IgM responses of aged rats when compared to controls (p = 0.049 and p = 0.007), respectively. In the young rats, while the IgG1 levels of control group were significantly higher than that of the melatonin group (p =0.021), IgM levels were not significantly different (p = 0.563). It is concluded that exogenous melatonin may augment the depressed humoral immune responses seen aged rats.

Role of photoperiod and the pineal gland in T cell-dependent humoral immune reactivity in the Siberian hamster

The present study tested the hypothesis that antibody production in response to xenoantigen is modulated by daylength and dependent upon the pineal gland. Alter injection of sheep erythrocytes (SRBC), serum immunoglobulin (Ig) concentrations were 5-fold lower in hamsters in short versus long days. Pinealectomy (Pinx) abolished the nocturnal melatonin rhythm, blocked short-day-mediated testis regression, and eliminated the short-day reduction in Ig production after SRBC treatment. Antibody titers in response to SRBC were equivalently augmented in short-day Pinx and long-day sham hamsters. The results indicate that photoperiodic effects on T cell-dependent humoral immunity are dependent upon the pineal gland. These findings raise the possibility that day length-associated changes in some immune system functions are mediated by the pineal melatonin rhythm.

Immunopathology of pineal glands from horses with uveitis

PURPOSE

Pinealitis accompanying uveitis is well established in laboratory models of experimental autoimmune uveoretinitis. In naturally occurring uveitis, pinealitis has been demonstrated in the pineal gland from a mare with active uveitis and is suspected in some human uveitides. We have evaluated pineal glands from horses with various stages of uveitis for signs of immunopathology accompanying spontaneous uveitis.

METHODS

Pineal glands from 10 horses with uveitis and from 13 horses without uveitis were evaluated for histochemical (H&E, collagen) and immunohistochemical (MHC class II antigen expression, infiltration of T and B lymphocytes, and glial fibrillary acidic protein (GFAP) and vimentin upregulation) evidence of inflammation.

RESULTS

Septal areas of pineal glands from horses with uveitis had clusters of MHC class II antigen-expressing cells, T lymphocytes, and enhanced collagen deposition. These changes were not as readily observed in pineal glands from horses without uveitis. B lymphocytes were detected only in the pineal gland from the one mare with active uveitis in which T and B lymphocytes were organized into follicles. No differences in GFAP or vimentin immunoreactivity were noted in pineal glands from horses with or without uveitis.

CONCLUSIONS

These pineal gland changes suggest that the pinealitis associated with equine uveitis is transient just as the uveitis of these horses is recurrent. Study of pineal glands from horses with clinically documented uveitis allows demonstration of subtle pineal changes associated with natural uveitis. Similar changes would be difficult to document in human patient populations.

Melatonin as a time-meaningful signal in circadian organization of immune response

Melatonin is synthesized and secreted during the dark period of the light/dark cycle. The rhythmic nocturnal melatonin secretion is directly generated by the circadian clock, located within the suprachiasmatic nuclei in mammals and is entrained to a 24-hour period by the light-dark cycle. The periodic secretion of melatonin may be used as a circadian mediator to any system that can 'read' the message. Melatonin seems to act as an arm of the circadian clock, giving a time-related signal to a number of body functions; one of these, the circadian organization of the defense of the organism, is discussed in some detail as an example.

Antigen-presenting cells in experimental autoimmune uveoretinitis

The present study attempts to identify the antigen-presenting cells in the retina, utilizing bone marrow-transplanted chimeric rats. Two types of chimeras were used: one produced by transplanting bone marrow cells from F1 hybrids of Lewis and Brown Norway (BN) into sublethally irradiated Brown Norway rats (LBN/F1-->BN), followed by adoptive transfer of S-antigen-specific T cells obtained from Lewis rats; the second produced by transplanting bone marrow cells from BN rats into sublethally irradiated F1 hybrids (BN-->LBN/F1), followed by adoptive transfer of S-antigen-specific T cells obtained from F1 hybrids. As controls, Lewis, F1 hybrids and BN rats also received adoptive transfer of syngeneic uveitogenic T cell lines. All animals were killed on the seventh day after adoptive transfer and their eyes and pineal glands were analysed immunohistochemically, utilizing antibody directed against Lewis specific MHC class II molecules(OX-3). The analyses revealed the development of uveoretinitis and pinealitis in both types of chimeras and in the Lewis and F1 hybrid rats. BN rats did not develop uveoretinitis. OX-3-positive cells were found in the retina and the pineal glands of both types of chimeras, and in the Lewis and F1 hybrid rats but not in the BN rats. These cells in the retina expressed dendritic morphology and perivascular distribution. Retinal pigment epithelia, Müller cells and the vascular endothelia of both chimeras, the two strains, and the F1 hybrid rats did not demonstrate OX-3-positive staining. These results suggest that the bone marrow-derived cells in the retina and pineal gland may present S-antigen to T cells, initiating the cascade of uveoretinitis and pinealitis.

I. Role of the pineal gland in multiple sclerosis: a hypothesis

Despite intensive research over the past several decades, the etiology and pathogenesis of multiple sclerosis (MS) remain elusive. The last 20 years have seen only meager advances in the treatment of the disease in part because too much attention has been devoted to the process of demyelination and its relationship to the neurologic symptoms and recovery of the disease. A host of biological phenomena associated with the disease involving interactions among genetic, environmental, immunologic, and hormonal factors, cannot be explained on the basis of demyelination and, therefore, require refocusing attention on alternative explanations, one of which implicates the pineal gland as the pivotal mover of the disease. This review summarizes the evidence linking dysfunction of the pineal gland with the epidemiology, pathogenesis, clinical manifestations, and course of the disease. The pineal hypothesis of MS also provided the impetus for the development of a novel and highly effective therapeutic modality, one that involves the transcranial application of AC pulsed electromagnetic fields in the picotesla flux density.

Anticancer neuroimmunomodulation by pineal hormones other than melatonin: preliminary phase II study of the pineal indole 5-methoxytryptophol in association with low-dose IL-2 and melatonin

Despite several years of experimental observations, the clinical application of the neuroimmunomodulation is still at the beginning. The pineal gland plays a main role in mediating the link between psychoneuroendocrine and immune systems. Melatonin (MLT), which is the main pineal hormone produced during the night, has appeared to amplify IL-2 anticancer activity. Other pineal hormones, however, would have immunomodulatory activity, in particular 5-methoxytryptophol (5-MTT), which is mainly produced during the light phase of the day. Previous clinical studies have shown that low-dose IL-2 plus MLT may have therapeutic efficacy in advanced cancer patients with neoplasms generally resistant to IL-2 alone, with a tumor regression rate generally less than 20% and an acceptable toxicity. The present study was carried out to evaluate the efficacy of low-dose IL-2 in association with both MLT and 5-MTT. The study included 14 untreatable advanced solid tumor patients (lung cancer: 4; gastric cancer: 3; mesothelioma: 2; hepatocarcinoma: 2; pancreatic cancer: 1; melanoma: 1; colon cancer: 1). IL-2 was injected subcutaneously at 3 MIU/day for 6 days/week for 4 weeks, by repeating a second cycle after a 21- day rest period. Both MLT and 5-MTT were given orally at 40 mg/day in the evening and at 1 mg/day at noon. The clinical results, as evaluated by WHO criteria after each cycle, consisted of partial response (PR) in 4/14 (29%) (lung cancer: 2; hepatocarcinoma: 1; mesothelioma: 1), stable disease (SD) in 6 and progressive disease in the last 4 patients. The treatment was extremely well tolerated in all patients, and in particular no fever greater than 38 degrees C occurred. These preliminary results show that the neuroimmunotherapy with low-dose IL-2 plus two pineal hormones, MLT and 5-MTT, is a well tolerated and potentially effective cancer therapy of untreatable advanced solid tumor patients, with results apparently superior with respect to those previously described with IL-2 plus MLT alone.

Immunohistochemical and tracer studies of macrophages/microglia in the pineal gland of postnatal rats

The pineal gland of rats of various ages (1-21 days old) was examined by immunohistochemistry and electron microscopy. Numerous widely distributed cells identified as macrophages/microglia were immunoreactive with the monoclonal antibodies OX-42, OX-18, OX-6, and ED1, indicating that they expressed complement type 3 (CR3) receptors, major histocompatibility complex class I and II antigens, and antigens of monocyte/macrophage lineage as detected by the antibodies, respectively. Following an intraperitoneal injection of rhodamine isothiocyanate (RhIC) in all age groups, the cells emitted a bright fluorescence. They were also labeled by horseradish peroxidase (HRP), as demonstrated in both light and electron microscopy. An HRP reaction was observed in vesicles and lysosomes at the ultrastructural level. A remarkable feature was the uptake of these tracers by pinealocytes. In light microscopy, the pinealocytes showed a punctate reaction product 3-24 hours after HRP injection. By electron microscopy, the reaction product was observed in vesicles, lysosomes, and some rod-like structures in the cytoplasm. On the basis of their immunophenotypic features, it is suggested that the macrophages/microglia in the pineal gland are active phagocytes which are also probably involved in the immunoregulatory function in the gland. The avid uptake of RhIC and HRP from the circulation by these cells suggests that serum-derived substances that may gain access to the parenchyma of the gland are being constantly monitored. The labeling of pinealocytes with HRP suggests that the functional activities of these cells are being modulated by serum-derived substances.

Melatonin and the immune-hematopoietic system therapeutic and adverse pharmacological correlates

The pineal neurohormone melatonin functionally synchronizes the photoperiod in the organism. In the last decade, it has become increasingly clear that the pineal gland and melatonin also play an important immunoregulatory role. T helper (Th) cells bear G-protein-coupled melatonin receptors. Activation of melatonin receptors enhances the release of Th cell cytokines, such as gamma-interferon and interleukin-2, as well as novel opioid cytokines which cross-react immunologically with both interleukin-4 and dynorphin B. These mediators may counteract secondary immunodeficiencies, protect mice against lethal viral and bacterial diseases, synergize with interleukin-2 in cancer patients and affect hematopoiesis. Hematopoiesis is apparently influenced by the action of melatonin-induced opioids on kappa-opioid receptors present on stromal bone marrow cells. Most interestingly, gamma-interferon and colony-stimulating factors may modulate the production of melatonin in the pineal gland. A hypothetical pineal-immune-hematopoietic network is, therefore, taking shape. From the immunopharmacological point of view, there is a need for clinical studies on the effect of melatonin in human immunodeficiency-virus-infected patients and cancer patients. In conclusion, melatonin seems to be an important immunomodulatory hormone which deserves to be further studied to identify its relevance in immune-based diseases, its therapeutic indications and its adverse effects.

[The participation of the epiphysis in the anti-stress protection of the brain]

Modern data on the functional features of epiphysis classify it as a cerebral stress-limiting structure. The anti-stress effect produced, first and foremost by melatonine, the main epiphysis hormone, is achieved through modification of the central neural mediation processes, synchronization of the circadian rhythmicity, optimization of the endocrine and immune status of an organism. Control of the stress-limiting activity is promising for alleviation of neuroses and psychic depressions.

A monoclonal antibody that specifically recognizes a novel mitochondrial protein of human astrocytes

We established a monoclonal antibody to human astrocytes using a human glial cell-rich fraction as the immunogen. The antibody, named PRAS-4, specifically labeled populations of astrocytes in a fine granular manner immunohistochemically. In formalin-fixed, paraffin-embedded tissue sections, PRAS-4-positive astrocytes were extensively distributed in the gray matter of the central nervous system, namely the cerebral cortex, basal ganglia, diencephalon, midbrain, various nuclei of the brain stem, cerebellar cortex and nuclei, and spinal cord. In the white matter, a few positive astrocytes were located mostly in the perivascular area. The reaction was lost after protease digestion and it resisted periodic acid, suggesting that the epitope is of a protein. The molecular weight of the antigen was estimated as 62 kDa. Ultrastructurally, the immunoreaction was localized on the outer and inner membranes of astrocytic mitochondria, and unlabeled mitochondria coexisted in the same cells. Extra-mitochondrial regions were not stained. PRAS-4 preferentially labeled astrocytes of the protoplasmic type, and may be applicable to studies on the development, specific functions and neoplasms of astrocytes.

Expression of class II MHC molecules in the rat pineal gland during development and effects of treatment with carbon tetrachloride

Cells expressing major histocompatibility complex (MHC) class II (Ia) antigen have been examined during the development of rat pineals and in the pineal gland of adult rats treated with carbon tetrachloride. Cells positive for MHC class II are first detected in the pineal gland of the 7-day-old rat. These positive cells increase in number gradually during development, MHC class II immunoreactivity reaching adult levels at 4 weeks after birth. The MHC class II antigen is intensely labeled on the cell surface, and labeled cells are distributed throughout the organ, several positive cells being gathered into groups. The positive cells are small (7-12 microm in diameter), irregular in shape, and frequently exhibit one or more processes. At the electron-microscopic level, the cytoplasm of positive cells contains few organelles, variously sized empty vacuoles, and a few electron-dense lysosome-like structures. Pinealocytes with synaptic ribbons have been found adjacent to immunoreactive cells. Double-immunoperoxidase staining for MRC OX6, MRC OX42, and ED1 results in OX6(-)/ED1(+)/OX42(+), OX6(-)/ED1(-)/OX42(+), and OX6(+)/ED1(-)/OX42(- )cells. These findings suggest that OX6-positive cells in the pineal can be considered as peripheral dendritic cells. The number of cells expressing MHC class II (Ia) antigen significantly increases in the pineal gland of rats after treatment with carbon tetrachloride (P<0.005). Our results indicate that at least some of the OX6-positive cells migrate into the gland from the circulation under these conditions.

Functional connections between the pineal gland and immune system

Experimental findings which support a functional connection between the pineal gland and immune system in mammals and birds are summarized. Developmental and age-related changes in pineal gland function appear, at least partially, to be related with immune system efficiency. Mechanisms whereby melatonin influences immune system function are complex, but include participation of mediators (endogenous opioids, cytokines, hormones, zinc pool) as well as specific binding sites on the immune cells. Melatonin, as a highly lyophilic compound, may also penetrate immune cells without mediation of specific receptors and act within as a potent free radical scavenger and as an anti-aging and oncostatic factor. The immune system may, in turn, via synthesis and secretion of soluble factors, cytokines, influence pineal gland function, thereby closing the information loop to maintain homeostasis in order to face the harmful environment.

The influence of season, photoperiod, and pineal melatonin on immune function

In addition to the well-documented seasonal cycles of mating and birth, there are also significant seasonal cycles of illness and death among many animal populations. Challenging winter conditions (i.e., low ambient temperature and decreased food availability) can directly induce death via hypothermia, starvation, or shock. Coping with these challenges can also indirectly increase morbidity and mortality by increasing glucocorticoid secretion, which can compromise immune function. Many environmental challenges are recurrent and thus predictable; animals could enhance survival, and presumably increase fitness, if they could anticipate immunologically challenging conditions in order to cope with these seasonal threats to health. The annual cycle of changing photoperiod provides an accurate indicator of time of year and thus allows immunological adjustments prior to the deterioration of conditions. Pineal melatonin codes day length information. Short day lengths enhance several aspects of immune function in laboratory studies, and melatonin appears to mediate many of the enhanced immunological effects of photoperiod. Generally, field studies report compromised immune function during the short days of autumn and winter. The conflict between laboratory and field data is addressed with a multifactor approach. The evidence for seasonal fluctuations in lymphatic tissue size and structure, as well as immune function and disease processes, is reviewed. The role of pineal melatonin and the hormones regulated by melatonin is discussed from an evolutionary and adaptive functional perspective. Finally, the clinically significance of seasonal fluctuations in immune function is presented. Taken together, it appears that seasonal fluctuations in immune parameters, mediated by melatonin, could have profound effects on the etiology and progression of diseases in humans and nonhuman animals. An adaptive functional perspective is critical to gain insights into the interaction among melatonin, immune function, and disease processes.