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Chemotherapy-induced peripheral neuropathy (CIPN) characterized by pain and numbness in hands and feet is a common side-effect of cancer treatment. In most patients symptoms of CIPN subside after treatment completion; however, in a substantial group CIPN can persist into survivorship. Mechanism(s) that regulate recovery from CIPN have not been studied. We investigated whether T lymphocytes play a role in regulating CIPN recovery. In WT and Rag1−/− mice mechanical hyperalgesia developed immediately following paclitaxel treatment but was significantly prolonged in Rag1−/− mice. When Rag1−/− mice were reconstituted with CD3+ T cells recovery was measured at rates comparable to WT mice. Next, we investigated if T lymphocytes are present in lumbar dorsal root ganglia (DRGs) that innervate the hind paws where hyperalgesia is measured. Increased numbers of CD3+ T lymphocytes were detected in lumbar DRGs of paclitaxel-treated mice when compared to vehicle-treated mice on day 7 and the majority were CD8+ T lymphocytes. Reconstitution of Rag1−/− mice with either CD8+ or CD4+ lymphocytes showed that only those mice that received CD8+ lymphocytes recovered from paclitaxel-induced neuropathy. Furthermore, blockade of IL-10 by intrathecal injection of anti-IL-10 antibody delayed recovery. Down-regulation of peripheral monocyte recruitment by anti-CCR2 antibody inhibited CD8+ T lymphocyte-mediated recovery as well suggesting that the interplay between CD8+ lymphocytes and monocytes is crucial for recovery from pac litaxel-induced neuropathy.

Neurotoxic side-effects of chemotherapy, including pain and numbness in hands and feet, frequently leads to dose reduction. This chemotherapy-induced peripheral neuropathy (CIPN) often persists long into survivorship and negatively affects quality of life. No drugs are available to prevent or treat CIPN and underlying mechanisms are only partially understood. Animal models for investigating chemotherapy-induced numbness are lacking. We have developed a tool for measuring numbness in mice; the adhesive removal task (ART). This task measures the time it takes an animal to show a behavioral response to an adhesive patch on its paw. We show that cisplatin induces mechanical hyperalgesia and impairs performance in the ART without altering general locomotor activity or motor coordination. Here we investigated the capacity of a specific histone deacetylase 6 (HDAC6) inhibitor to treat cisplatin-induced numbness and pain in mice. We show that the HDAC6 inhibitor, ACY-1083, effectively treats cisplatin-induced numbness. ACY-1083 also reverses existing cisplatin-induced mechanical hyperalgesia. ACY-1083 alone did not affect sensitivity to mechanical stimulation or performance in the ART. Analysis of cultured dorsal root ganglia revealed that cisplatin treatment decreased mitochondrial axonal transport, while co-culture with ACY-1083 attenuated this decrease. This is important because HDAC6 acts by deacetylating alpha-tubulin, which is thought to promote axonal transport. To our knowledge this is the first identified drug capable of treating already existing chemotherapy-induced numbness and pain.

The crucial clinical problem in leprosy is the occurrence of acute inflammatory episodes that lead to nerve damage, even after the infecting organisms have been killed by antibiotics. We suggest that the instability of these inflammatory sites is attributable to a disturbance of the role that nerves play in the regulation of inflammation. The destruction of sensory C fibers and sympathetic innervation will remove anti-inflammatory feedback circuits. Moreover, diminishing levels of neuropeptides and changes in the cytokine profile will affect the cortisol-sensitivity of infiltrating T cells, and modulate the cortisol-cortisone shuttle so that the inflammatory site becomes resistant to physiological levels of anti-inflammatory adrenocortical steroids.

The mechanisms underlying the transition from acute to chronic pain remain poorly understood. In mice, reduced expression of G protein-coupled receptor kinase 2 (GRK2) in pain sensing neurons promotes cAMP signaling to the guanine nucleotide exchange factor EPAC1 and prolongs the PGE2-induced increase in pain sensitivity (hyperalgesia). Using models of inflammatory pain, we showed that transition to chronic pain is associated with reduced GRK2 and/or increased EPAC1 in dorsal root ganglion (DRG) neurons In addition, when we either increased GRK2 in vivo by viral-based gene-transfer or decreased EPAC1 in vivo, as was the case for mice heterozygous for Epac1 or mice treated with Epac1 antisense-oligodeoxynucleotides, the transition to chronic pain was prevented. In search for the mechanism that promotes Epac1 signaling when GRK2 is low, we identified GRK2 as the first kinase known to phosphorylate Epac1. We identified the residue in Epac1 that is phosphorylated by GRK2 and demonstrated that phosphorylation of this residue in Epac1 inhibits Epac-mediated activation of the small G protein Rap1 and agonist-induced membrane association of Epac1. These findings identify Epac1 as a non-G protein coupled receptor GRK2 substrates and further establish the key role of GRK2 in pain sensing neurons in protecting against chronic inflammatory pain. Our data suggest that therapies targeted at balancing nociceptor GRK2 and EPAC1 levels have promise for the prevention and treatment of chronic pain.

Chemotherapy-induced peripheral neuropathy (CIPN) characterized by loss of sensory sensitivity and pain in hands and feet is the major dose-limiting toxicity of many chemotherapeutics. There are no FDA-approved treatments for CIPN. The anti-diabetic drug metformin inhibits pathological pain following nerve injury in mice and rats. We tested the hypothesis that metformin protects against chemotherapy-induced neuropathic pain and sensory deficits in mice. Mice were treated with cisplatin together with metformin or saline. Co-administration of metformin almost completely prevented the cisplatin- and paclitaxel-induced mechanical allodynia. Cisplatin decreased the time to detect an adhesive patch on the hind paw, a novel indicator of sensory deficits. Reduced sensory function was prevented by co-administration of metformin. Moreover, metformin prevented cisplatin-induced loss of IENFs in the hind paw. In the spinal cord, metformin treatment altered glial activation, indicating a contribution of regulation of neuroinflammation to the protective effect. In conclusion, metformin protects against pain and loss of sensory function in a mouse model of CIPN. The mechanism involves reduced peripheral nerve damage and changes in neuroinflammation, strongly suggesting that metformin exerts a neuroprotective effect. Because metformin is widely used for treatment of type II diabetes, has a broad safety profile and is currently being tested as an adjuvant drug in cancer treatment, clinical translation of these findings could be rapidly achieved.

Chemotherapy-induced peripheral neuropathy (CIPN) occurs in about 60% of cancer patients undergoing treatment. With no FDA-approved drugs to treat CIPN, a significant number of patients receive sub-optimal anti-cancer treatment. Damage to mitochondria in peripheral sensory neurons contributes to mechanical hyperalgesia in rodent models of CIPN. In this study we investigated if a mitochondrial protectant, Pifithrin-μ (PFT-μ), prevented CIPN both during and after completion of chemotherapy. In mice treated with paclitaxel alone increased hyperalgesia was present both during and after completion of chemotherapy. In mice treated with PFT-μ systemically (intraperitoneal-i.p) alone or in combination with paclitaxel, mechanical hyperalgesia was not measured both during and after completion of chemotherapy. Administration of PFT- μ intrathecally (i.t.) was also protective against CIPN, with no measurement of hyperalgesia throughout treatment. These data demonstrate that administration of PFT-μ (i.p. or i.t.) prevents CIPN. One of the potential risks of treating CIPN with PFT-μ is that it may interfere with cancer treatment. To investigate this we co-cultured human ovarian tumor cells with paclitaxel alone or in combination with PFT-μ. Significant paclitaxel-induced tumor cell death was measured when tumor cells were cultured with paclitaxel alone or in combination with PFT-μ. These data demonstrate that PFT-μ does not interfere with paclitaxel-induced tumor cell death. This study found that PFT-μ is a potential therapeutic for preventing CIPN thereby improving quality of life in cancer survivors.

Chemotherapy-induced peripheral neuropathy (CIPN) is the major dose-limiting toxicity for cancer treatment. In this study we investigated the contribution of T cells in the course of CIPN. Wild type (WT; C57Bl6J) and T cell-deficient mice (Rag1−/−) were treated with chemotherapy (paclitaxel) and mechanical hyperalgesia was measured. Mechanical hyperalgesia developed immediately following treatment in WT and Rag1−/− mice. In WT mice paclitaxel-induced mechanical hyperalgesia resolved 14 days after treatment. However, in Rag1−/− mice mechanical hyperalgesia persisted for more than 21 days. When T cells (CD3+) were transferred into Rag1−/− mice paclitaxel-induced mechanical hyperalgesia resolved by 14 days. These data demonstrate that T cells are critical for resolution from CIPN. Paclitaxel administration has been shown to damage peripheral sensory neuron cell bodies located in dorsal root ganglia (DRGs). Immunohistochemistry analysis revealed that the transferred T cells localized to (DRGs) in Rag1−/− mice. Next, we investigated if a single T cell subset was responsible for resolution from CIPN. Transfer of CD8+ T cells into Rag1−/− mice was sufficient to normalize resolution of paclitaxel-induced mechanical hyperalgesia by 14 days. In contrast when Rag1−/− mice were injected with CD4+ T cells mechanical hyperalgesia persisted for up to 21 days. How CD8+ T cells regulate resolution from CIPN is under investigation, nevertheless this is the first study to our knowledge to identify a beneficial role for CD8+ T cells in CIPN.

The nervous, endocrine, and immune systems are intimately connected through mutually acting regulatory systems. The immune system is highly specialized in its recognition of and reaction to specific antigens from internal as well as external sources. The brain is specialized in recognition and response to internal and external emotional and physical stimuli. Both systems have their own characteristic responses to these stimuli. However, the response patterns of the two systems are partly overlapping, that is, they both produce mediators such as cytokines and neuropeptides that can act as communication pathways for the two systems. Moreover, the immune system expresses receptors or binding sites for every neurotransmitter or hormone tested so far, thereby enabling the immune system to recognize and to respond to neuroendocrine signals (Blalock & Smith, 1985).

Autoimmune disease is the result of an immune reaction directed against components of the body, leading to tissue damage and organ dysfunction. Autoimmune diseases comprise a wide spectrum of diseases with, as a common factor, a chronic response against autoantigens. The etiopathogenesis of autoimmune diseases is not completely understood. Genetic predisposition associated with HLA haplotypes, inducing factors like inflammatory processes including molecular mimicry and dysregulation of the immune response, all contribute. Sex-related differences in the prevalence of autoimmune diseases have been recognized for a long time. More recent evidence derived predominantly from animal models suggests that the reactivity of the hypothalamus-pituitary-adrenal (HPA) axis system may also be a major factor in determining susceptibility to the development of an autoimmune disease. In addition, it has become evident that, during the course of an autoimmune disease, alterations in the interaction between the neuroendocrine and immune systems take place on the level of expression of receptors for neuroendocrine mediators.

Chronic pain is a major clinical problem, and understanding mechanisms underlying the transition from acute to chronic pain is needed. We investigated the contribution of peripheral monocytes/macrophages to the transition from acute to persistent IL-1beta induced hyperalgesia. As a model, we used LysM-GRK2+/− mice that develop prolonged hyperalgesia in response to IL-1β due to a cell specific reduction in G protein-coupled receptor kinase 2 (GRK2) in lysozyme M-positive microglia/macrophages. In wild type (WT) mice, peripheral monocyte/macrophage depletion prolonged intraplantar IL-1β -induced hyperalgesia from 8 days. In LysM-GRK2+/− mice that develop persistent IL-1β hyperalgesia, monocyte/macrophage depletion did not have any effect. Adoptive transfer of WT bone marrow derived monocytes (BMDM), but not of GRK2+/− BMDM, to LysM-GRK2+/− mice prevented the transition to persistent IL-1β-induced hyperalgesia. In search for the mechanism, we show that GRK2-deficient macrophages produce less IL-10 in vitro and intrathecal IL-10 adminisration attenuated IL-1β-induced hyperalgesia in LysM-GRK2+/− mice. Moreover, in WT mice intrathecal anti-IL10 prolonged IL-1β-induced hyperalgesia. Finally, adoptive transfer of IL-10−/− BMDM did not normalize the IL-1β-induced hyperalgesia in LysM-GRK2+/− mice. In conclusion, we uncovered a key role for peripheral monocytes/macrophages in promoting resolution of inflammatory hyperalgesia via a mechanism dependent of IL-10 signaling. The decreased capacity of GRK2-deficient monocytes/macrophages to produce IL-10 underlies their inability to promote resolution of inflammatory pain. Supported by NIH grants NS073939 and NS074999.

Chronic pain and depression frequently co-occur. We used the spared nerve injury (SNI) model of neuropathic pain in mice to explore the neuroimmune mechanism of the comorbidity of neuropathic pain and depressive-like behaviors. SNI induces both mechanical hyperalgesia and depressive-like behavior assessed as reduced social interaction and increased immobility in the forced swim test. These behavioral responses were associated with increased IL-1beta mRNA in the contralateral frontal cortex, ipsilateral lumbar dorsal horn and liver. Daily intrathecal injection of IL-1RA inhibited mechanical hyperalgesia and depressive-like behavior. IL-1RA also abrogated SNI-induced increases IL-1beta and in microglial activation. Peripheral inflammation-induced depressive-like behavior is mediated via increased expression of the indoleamine 2,3-dioxygenase1(IDO1), which catalyzes the conversion of tryptophan to kynurenine. SNI surgery increases the kynurenine/tryptophan ratio in plasma. Concomitantly, IDO1 mRNA expression was increased in liver but not in brain or spinal cord. Intrathecal IL-1RA prevented the increase in liver IDO1mRNA in SNI mice. Importantly, genetic deletion of IDO1 prevented the SNI-induced depressive like behaviors without affecting the pain response. Spinal cord IL-1β signaling is key for both SNI-induced pain and depressive-like behaviors. In contrast, IDO1 activity only contributes to SNI-induced depressive behaviors. Our finding that SNI induces an increase in IDO1 in the liver and not in the brain indicates that IDO controls SNI-induced depressive-like behavior through a peripheral-to-brain pathway. Supported by NIH grants NS083939 and NS074999.

During subarachnoid hemorrhage (SAH) blood flows into the subarachnoid space of the brain as a result of a ruptured blood vessel. The mortality rate of SAH is approximately 40–50% and surviving patients are confronted with a great loss of quality of life. SAH occurs at a relatively young age and has an unpredictable onset. There are only limited therapeutic options and unfortunately these treatments have a short time window. We studied the therapeutic effects of intranasal mesenchymal stem cell transplantation (MSC) in the endovascular puncture model in the rat. SAH induces long-term brain damage through loss of grey and white matter which is located mainly in the cortex. Moreover, SAH is associated with cerebral inflammation as shown by cytokine mRNA expression and microglia/astrocyte activation 3 weeks after SAH. Furthermore, sensory motor function as observed in the adhesive removal test was decreased as well as mechanical sensitivity of the hind paws as shown by von Frey testing. Interestingly, SAH also decreased sucrose preference. Intranasal administration of MSC 6 days after SAH decreased brain lesion volume and downregulated cerebral inflammation. MSC treatment improved sensori-motor behavior and mechanical sensitivity of the paws. Moreover, sucrose preference was restored to the level of sham-operated animals. Conclusion: Intranasal MSC transplantation restores brain damage, and sensori-motor function and reduces longterm cerebral inflammation and depressive-like behavior in animals subjected to SAH.

Mesenchymal stem cell (MSC) administration via the intranasal route could become an effective therapy to treat neonatal hypoxic-ischemic (HI) brain damage. We analyzed long-term effects of intranasal MSC treatment on lesion size, sensorimotor and cognitive behavior, and determined the therapeutic window and dose response relationships. Furthermore, the appearance of MSCs at the lesion site in relation to the therapeutic window was examined. Nine-day-old mice were subjected to unilateral carotid artery occlusion and hypoxia. MSCs were administered intranasally at 3, 10 or 17 days after hypoxia-ischemia (HI). Motor, cognitive and histological outcome was investigated. PKH-26 labeled cells were used to localize MSCs in the brain. We identified 0.5 × 10(6) MSCs as the minimal effective dose with a therapeutic window of at least 10 days but less than 17 days post-HI. A single dose was sufficient for a marked beneficial effect. MSCs reach the lesion site within 24 h when given 3 or 10 days after injury. However, no MSCs were detected in the lesion when administered 17 days following HI. We also show for the first time that intranasal MSC treatment after HI improves cognitive function. Improvement of sensorimotor function and histological outcome was maintained until at least 9 weeks post-HI. The capacity of MSCs to reach the lesion site within 24 h after intranasal administration at 10 days but not at 17 days post-HI indicates a therapeutic window of at least 10 days. Our data strongly indicate that intranasal MSC treatment may become a promising non-invasive therapeutic tool to effectively reduce neonatal encephalopathy.

Publisher Summary This chapter discusses corticotropin-releasing hormone and proopiomelanocortin-derived peptides in the modulation of immune function. Corticotropin-releasing hormone (CRH) is a 41 amino acid peptide that is mainly synthesized in the paraventricular nucleus of the hypothalamus. It induces the release of proopiomelanocortin (POMC) in the anterior pituitary. In the pituitary, POMC is cleaved enzymatically into various peptides such as adrenocorticotropic hormone (ACTH) and the endogenous opioid β-endorphin. The fact that CRH is produced in multiple sites in the body suggests that the action of CRH is not restricted to the pituitary. Evidence has been obtained for the presence of POMC-inducing activity in cells of the placenta and in Sertoli cells. There have to be at least two types of endorphin receptors on lymphocytes, one with high and the other with low affinity for the neuropeptide. In vivo, the high-affinity receptor site should be occupied constantly, owing to the binding of pituitary-derived circulating β-endorphin. The presence of such a receptor is in accordance with in vitro data. When lymphocytes are tested for β-endorphin reactivity in vitro, effects of the peptide can be observed in the low picomolar range. The second type of receptor has a lower affinity and should be capable of binding the endorphin secreted by the lymphocyte after activation by antigen or IL-1. The low-affinity receptor has been shown to have an affinity constant of 10-9 M and to be present on activated lymphocytes.

Effects of Early Neonatal Dexamethasone Treatment on Susceptibility to Experimental Autoimmune Encephalomyelitis (EAE) and on the LPS-Induced Corticosterone Response in Adult Rats

We intended to investigate whether the suppression of antigen-induced antibody responses in vitro in man by T suppressor cells required contact of T suppressor cells with target cells or whether this effect was mediated by factors released by T suppressor cells. To this end supernatants of antigen-induced T suppressor cells were tested (by a plaque forming cell assay) for their capacity to suppress antibody responses of autologous and allogeneic human peripheral blood lymphocytes. We have shown that supernatants of antigen-specific T suppressor cells, designated as TsF24: a) can suppress an antibody response of autologous but not allogeneic lymphocytes to the inducing antigen; b) are antigen-specific in their effect; and 3) are produced by radiosensitive T cells. Furthermore, the target of the factor is a radiosensitive T cell. These findings taken together indicate that, in the generation of T-effector suppressor cells in man, T-T interactions occur, and in addition, that cellfree factors may be involved in these interactions.

The capacity of the peripheral blood lymphocytes (PBL) to generate an antibody response in vitro T cell-dependent antigen ovalbumin was studied in 12 severe hemophilia patients who were otherwise in good health. PBL from four of 12 patients were not capable of generating such a response after stimulation in vitro, whereas all controls were normal. This negative plaque-forming cell (PFC) response coincided with the presence of antibodies directed toward human T-lymphotropic virus III/lymphadenopathy-associated virus (HTLV-III/LAV). Only one patient with antibodies against HTLV-III/LAV had a normal PFC response. The negative PFC response was not due to a deficient T helper cell activity, nor to an excessive T suppressor cell function. However, in the peripheral blood of these four patients, the presence of activated B cells that are refractory to antigen-specific T helper cell signals and secrete specific antibodies spontaneously could be demonstrated. Most of the patients showed a hyperimmunoglobulinemia. No correlation between the T4/T8 ratio and the level of the PFC response was demonstrable. From the data obtained in these investigations we raise the hypothesis that infection with HTLV-III/LAV in hemophilia patients will lead to in vivo (pre)activation of B cells that results in unresponsiveness or decreased response to antigen-specific signals.

In human immune deficiency virus (HIV)-seropositive hemophilia patients, a low number of CD4 + lymphocytes is found, as well as a low CD4+/CD8+ ratio. In previous studies, it has been shown that antigen- specific T-helper cell (CD4+) function was present and no excessive antigen-specific T-suppressor cell (CD8+) function could be demonstrated. In this report, we studied another activity of CD4+ cells, namely the capacity to induce T-suppressor cell activity. The results clearly show a selective dysfunction of CD4+ suppressor-inducer (Tsi) cell function. Since these HIV-seropositive hemophilia patients showed the presence of activated B cells in the peripheral circulation refractory to antigen-specific T-helper cell signals and secreting specific antibodies spontaneously, we raised the hypothesis that the activated B cells in the patients activate the Tsi cells in vivo. This constant activation leads to a functional exhaustion of the Tsi cell pool.

STUDIES in animal models, in particular that of the murine system, have revealed that the sequence of events leading to an antibody response is similar to other complex biological processes in that they are controlled by interrelated regulatory mechanisms1,2. In man helper activity which regulates the antigen-induced antibody response in vitro is initiated by T lymphocytes bearing receptors for the Fc fragment of IgM (Tμ+ cells), whereas suppressive activity can be induced in T cells capable of binding the Fc fragment of IgG (Tγ+ cells)3. We present here data which indicate that Tμ+ cells, apart from providing help in the human antigen-driven process of B-cell activation, are also capable, in certain conditions, of inducing a subpopulation of unprimed T cells to suppress an antigen-induced antibody response.

In 47 patients undergoing open-heart surgical procedures, the influence of cardiopulmonary bypass (CPB) on lymphocyte function was investigated by studying in vitro the mitogen responses of lymphocytes in whole blood cultures. Subnormal mitogen responses before operation that likely resulted from dexamethasone medication were found in half of the patients studied. During operation, changes in phytohemagglutinin responses were uniform in a group of 23 patients. No significant effect of anesthesia and operation was observed until the patients were heparinized (i.e., before CPB). At the end of operation, the phytohemagglutinin response was below normal. In a group of 24 other patients, postoperative mitogen responses were studied. A tendency toward restoration of mitogen responses was observed in most patients the first morning after operation. However, no uniform pattern of normalization of mitogen responses was found. In an attempt to relate postoperative mitogen responses to trauma resulting from CPB, we observed that perioperative (in comparison with postoperative) administration of blood coincided with a significantly higher incidence of subnormal phytohemagglutinin and pokeweed mitogen responses on postoperative day 1. No correlation between laboratory data and clinical findings could be established.

Publisher Summary This chapter explores human B cell activation in vitro. In a study described in the chapter, the the Tγ-enriched, the Tγ-depleted, and the Tμ-enriched cells were isolated by rosetting. The regulatory effects on the antigen-induced PFC response were tested using the method of Dosch and Gelfand. To test helper cell activity, the various T cell fractions were cultured with B cells, 5% adherent cells, and either 5 × 10 6 sheep red-blood cells (SE)/culture or 3 μg Ovalbumin (OA)/ml of culture medium. It was demonstrated that the helper activity is residing in the Tγ depleted- and the Tγ-enriched fraction. It was also demonstrated that peripheral blood T cells expressing helper function in the antigen-induced antibody response are located in the Tμ cell subpopulation, whereas T suppressor function is exerted by T cells present in the Tγ subpopulation. These subpopulations differ in their sensitivity toward irradiation. The activity of T helper cells can be replaced in vitro by a T cell factor that is released into the medium after 120 h of culture.

Mononuclear cells isolated from human cord blood (CBL) of full-term neonates were stimulated in vitro with a dose range of T cell-dependent antigens, i.e. ovalbumin or sheep erythrocytes, and tested for the capacity to mount an antigen-specific plaque-forming cell (PFC) response. Both of the antigens used induced in CBL a PFC response with the same kinetics of PFC formation and of the same magnitude as found in cultures of adult peripheral blood lymphocytes (PBL). However, optimal PFC responses in CBL were obtained at a hundredfold lower concentration of the antigens compared with the optimal antigen doses for the induction of a PFC response in adult PBL. This phenomenon was further investigated with respect to the antigen dose dependency of the activation of neonatal B cells and neonatal regulatory T cells. The induction of a PFC response in CBL at antigen concentrations that were suboptimal for adult PBL showed a correlation with the particular antigen dose requirements for the activation of B cells and T helper cells in neonates. Furthermore, the findings suggest that the decrease of the PFC response in CBL stimulated with supraoptimal doses of antigen was not caused by the induction of unresponsiveness at the B cell level or by interference of pregnancy-associated substances with the PFC response, but was rather the result of the activation of antigen-specific T suppressor cells. Neonatal T suppressor cells were activated at antigen concentrations that generated T helper activity in the adult. Thus, although neonatal B cells possess the intrinsic capacity to mature into antigen-specific PFC, the conditions for effective activation of neonatal T cells regulating the B cell response differ from those for the activation of adult regulatory T cells.

There is ample evidence that the immune response in man is regulated, although not exclusively, by T cells which have the capacity to induce, amplify or suppress the reactivity of the immune system. Analogous to the situation in the mouse, these various regulatory T cell functions are exerted by lymphocytes residing in distinct T cell subpopulations (1,2). These subsets can be recognized by distinct surface markers such as receptors for Fc fragments of different immunoglobulin isotypes (3) and cell surface structures defined by monoclonal antibodies (4).

There is ample evidence that the course of an immune response can be modulated by the central nervous system [1]. In this respect it is interesting that psychosocial factors have been described to influence immune function [1,2]. It is most likely that the hypothalamic-pituitary-adrenal axis is involved, and this indeed has been documented. However, also neurotransmitters and neuropeptides are known to be able to modulate immune reactivity [2]. Since stress may induce increased levels of hormones such as ACTH, prolactin, growth hormone and β-LPH, studies have been carried out to analyse the effect of these proteins on immune functions. Lately several reports have been published on the effect of neuropeptides, like enkephalins and endorphins on lymphocyte activities. Thus it has been reported by Johnson et al. [3] that α-endorphin (αE) suppresses the primary antibody response of murine spleen cells to sheep erythrocytes in vitro. The present study extends these findings, obtained in an animal model, towards immunomodulation of the antibody response of human peripheral blood B lymphocytes by αE.

Distinct human T-cell subpopulations were isolated and cultured in the presence of B-cells and antigens. After an incubation period of 6 days cells were tested for their capacity to secrete antigen-specific antibodies in the PFC-assay. The results indicate that the T-helper activity for the antigen-induced T-dependent B-cell differentiation is located in the Tμ-subpopulation, whereas the suppressor-cell activity is confined to the Tγ-subpopulation.

Subarachnoid hemorrhage (SAH) represents a considerable health problem. To date, limited therapeutic options are available. In order to develop effective therapeutic strategies for SAH, the mechanisms involved in SAH brain damage should be fully explored. Here we review the mechanisms of SAH brain damage induced by the experimental endovascular puncture model. We have included a description of similarities and distinctions between experimental SAH in animals and human SAH pathology. Moreover, several novel treatment options to diminish SAH brain damage are discussed. SAH is accompanied by cerebral inflammation as demonstrated by an influx of inflammatory cells into the cerebral parenchyma, upregulation of inflammatory transcriptional pathways and increased expression of cytokines and chemokines. Additionally, various cell death pathways including cerebral apoptosis, necrosis, necroptosis and autophagy are involved in neuronal damage caused by SAH. Treatment strategies aiming at inhibition of inflammatory or cell death pathways demonstrate the importance of these mechanisms for survival after experimental SAH. Moreover, neuroregenerative therapies using stem cells are discussed as a possible strategy to repair the brain after SAH since this therapy may extend the window of treatment considerably. We propose the endovascular puncture model as a suitable animal model which resembles the human pathology of SAH and which could be applied to investigate novel therapeutic therapies to combat this debilitating insult.