Production of interferon-gamma in families with multiple occurrence of schizophrenia

B-cells and schizophrenia: A promising link or a finding lost in translation?

Recent genetic studies have suggested a potential role for B-cells in the pathogenesis of schizophrenia. Greater insight in the functioning of B-cells in patients with schizophrenia is therefore of importance. In this narrative review we aim to give an overview of the current literature on B-cells and schizophrenia. We found no evidence for altered numbers of these cells in blood. We did find support for increased levels of B-cell related cytokines and certain autoantibodies. Studies on B-cell development and function, or their numbers in cerebrospinal fluid or brain tissue are very limited. Based on the available data we appraise whether various B-cell mediated pathological mechanisms are likely to play a role in schizophrenia and provide directions for future research.

The Microbiome: A New Target for Research and Treatment of Schizophrenia and its Resistant Presentations? A Systematic Literature Search and Review

Background: The gastrointestinal system hosts roughly 1,800 distinct phyla and about 40,000 bacterial classes, which are known as microbiota, and which are able to influence the brain. For instance, microbiota can also influence the immune response through the activation of the immune system or through the release of mediators that are able to cross the brain blood barrier or that can interact with other substances that have free access to the brain, such as tryptophan and kynurenic acid, which is a metabolite of tryptophan and which has been involved in the pathogenesis of schizophrenia. Objectives: This paper reviews the possible relationships between microbiome, schizophrenia and treatment resistance. Given the possibility of a role of immune activation and alterations, we also describe the relationship between schizophrenia and immune inflammatory response. Finally, we report on the studies about the use of probiotic and prebiotics in schizophrenia. Methods: Cochrane library and PubMed were searched from the year 2000 to 2018 for publications about microbiome, immune-mediated pathology, schizophrenia and neurodevelopmental disorders. The following search string was used: (microbiome or immune mediated) AND (schizophrenia OR neurodevelopmental disorder). Associated publications were hand-searched from the list of references of the identified papers. A narrative review was also conducted about the use of probiotics and prebiotics in schizophrenia. Results: There exists a close relationship between the central nervous system and the gastrointestinal tract, which makes it likely that there is a relationship between schizophrenia, including its resistant forms, and microbiota. This paper provides a summary of the most important studies that we identified on the topic. Conclusions: Schizophrenia in particular, remain a challenge for researchers and practitioners and the possibility of a role of the microbiome and of immune-mediated pathology should be better explored, not only in animal models but also in clinical trials of agents that are able to alter gut microbiota and possibly influence the mechanisms of gastrointestinal inflammation. Microbiome targeted treatments have not been well-studied yet in patients with mental illness in general, and with schizophrenia in particular. Nonetheless, the field is well worth of being appropriately investigated.

Inflammation in Schizophrenia: Cytokine Levels and Their Relationships to Demographic and Clinical Variables

OBJECTIVE

Inflammation may play a role in the accelerated physical aging reported in schizophrenia, though biomarker findings and associations with demographic and clinical factors are inconsistent.

METHODS

In a cross-sectional, case-control design, 95 outpatients with schizophrenia (mean age ± SD: 48.1 ± 10.2 years) and 95 demographically comparable healthy comparison subjects (HCs) (mean age ± SD: 48.1 ± 12.1 years) were studied. Sociodemographic and clinical data were collected, and plasma levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interferon-γ (IFN-γ) were assayed. The authors compared cytokine levels, examined demographic and clinical associations, and adjusted for relevant variables with linear models.

RESULTS

Individuals with schizophrenia had higher levels of TNF-α and IL-6 but not IFN-γ than HCs. Age was not related to cytokine levels, and age relationships did not differ between diagnostic groups. Women had higher levels of IL-6. TNF-α and IL-6 levels were significantly correlated with depressive symptoms, and adjustment for depression reduced the group effect for both. Within the HCs, TNF-α levels were associated with physical comorbidity and body mass index. IL-6 levels were significantly correlated with body mass index and within schizophrenia patients, with worse mental and physical well-being. Accounting for physical morbidity and mental well-being reduced group differences in TNF-α and IL-6 levels, respectively. Worse positive symptoms were associated with higher IL-6 levels.

CONCLUSION

Higher TNF-α and IL-6 levels in schizophrenia patients were associated with depression, physical comorbidity, and mental well-being. Further longitudinal studies are warranted to assess inflammation as a potential treatment target for a subgroup of schizophrenia.

Pro-inflammatory cytokines and their epistatic interactions in genetic susceptibility to schizophrenia

Background

In schizophrenia, genetic background may provide a substrate for intrinsic maldevelopment of the brain through environmental influences, by recruiting neurotrophic factors and cytokines, to trigger the changes that lead to impaired neuronal functions. Cytokines being the key regulators of immune/inflammatory reactions are also known to influence the dopaminergic, noradrenergic, and serotonergic neurotransmission. Therefore, functional polymorphisms in cytokine genes may result in imbalances in the pro- and anti-inflammatory cytokine production.

Methods

We screened polymorphisms in pro- and anti-inflammatory cytokine genes using a case-control association study in a South Indian population. The role of allele, genotype, haplotype, and diplotypes of these cytokine genes and their epistatic interactions were assessed in contributing to the risk of developing schizophrenia. Meta-analysis for the reported associations was also monitored for global significance.

Results

The pro-inflammatory cytokine gene polymorphisms in IL1Ars1800587, IL6rs1800796, TNFArs361525, and IFNGrs2069718 were associated with schizophrenia. The study also provides significant evidence for strong epistatic interactions among pro-inflammatory cytokine genes IL6 and IFNG in the development of schizophrenia. In silico analysis suggested that associated risk variants were indicative of altered transcriptional activity with higher production of IL1α, IL-6, TNF-α, and IFN-ɤ cytokines. Meta-analysis indicated heterogeneity among study population while IL1Ars1800587 was found to be globally significant.

Conclusions

It is important to identify the nature of inflammatory response that can be amplified by the environment, to influence either Th1 response or Th2 response. The associated functional variants in the study are involved with increased expression resulting in higher production of the pro-inflammatory cytokines IL-1α, IL-6, TNF-α, and IFN-γ. The interaction of immunological stressors with these high producer alleles of pro-inflammatory cytokines may suggest that even a lower threshold may be sufficient to induce a resultant chronic effect on the psycho-social and environmental stressors that may result in the development and pathogenesis of schizophrenia. Understanding environmental factors that influence the expression of these pro-inflammatory cytokine genes or their interaction can possibly help in dissecting the phenotypic variation and therapeutic response to antipsychotics in schizophrenia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0569-8) contains supplementary material, which is available to authorized users.

Role of T helper lymphokines in the immune-inflammatory pathophysiology of schizophrenia: Systematic review and meta-analysis

BACKGROUND

Schizophrenia is highly complex multifactorial psychiatric disorder with poorly defined etiopathophysiology, which also has manifestations in the immune system.

AIMS

The aim of this review is to meta-analyze the available evidence regarding the role of immune activation indicated by the T helper cells in order to evaluate etiopathophysiological links between the immune system and schizophrenia.

METHODS

A literature search was performed in multiple electronic databases for relevant research papers published between 1990 and May 2014. Meta-analyses were conducted under both random- (REM) and fixed-effect models (FEM) by calculating weighted mean differences with 95% confidence intervals. Heterogeneity was assessed with the I(2) index.

RESULTS

Twenty-one studies were selected after observing inclusion and exclusion criteria. In vitro interferon-gamma (INF-γ) and interleukin (IL)-2 production was significantly lower in the schizophrenic patients compared with non-schizophrenic control individuals under both FEM and REM. Serum levels of IL-2 and serum/in vitro IL-4 were not significantly different in both groups under both FEM and REM. Overall Th1:Th2 ratio (INF-γ:IL-4 and IL-2:IL-4) in the serum samples was significantly deflected towards Th2 under both models in the serum samples (- 0.33 [- 0.59 to - 0.06]; P < 0.03, FEM and - 2.44 [- 4.27 to - 0.60]; P < 0.009, REM) but in vitro production Th1:Th2 ratio (INF-γ:IL-4 and IL-2:IL-4) was deflected towards Th1 under both the models (1.11 [0.45-1.78]; P < 0.002, FEM and 6.68 [0.72-12.64]; P < 0.03, REM).

CONCLUSIONS

Whereas the Th1:Th2 ratio in the serum samples deflected towards T2, in vitro Th1:Th2 ratio favored Th1 when the individual study data were meta-analyzed.

Antipsychotics-induced metabolic alterations: focus on adipose tissue and molecular mechanisms

The use of antipsychotic drugs for the treatment of mood disorders and psychosis has increased dramatically over the last decade. Despite its consumption being associated with beneficial neuropsychiatric effects in patients, atypical antipsychotics (which are the most frequently prescribed antipsychotics) use is accompanied by some secondary adverse metabolic effects such as weight gain, dyslipidemia and glucose intolerance. The molecular mechanisms underlying these adverse effects are not fully understood but have been suggested to involve a dysregulation of adipose tissue homeostasis. As such, the aim of this paper is to review and discuss the role of adipose tissue in the development of secondary adverse metabolic effects induced by atypical antipsychotics. Data analyzed in this article suggest that atypical antipsychotics may increase adipose tissue (particularly visceral adipose tissue) lipogenesis, differentiation/hyperplasia, pro-inflammatory mediator secretion and insulin resistance and decrease adipose tissue lipolysis. Consequently, patients receiving antipsychotic medication could be at risk of developing obesity, type 2 diabetes and cardiovascular disease. A better knowledge of the impact of these drugs on adipose tissue homeostasis may unveil strategies to develop novel antipsychotic drugs with less adverse metabolic effects and to develop adjuvant therapies (e.g. behavioral and nutritional therapies) to neuropsychiatric patients receiving antipsychotic medication.

A systematic, quantitative review of blood autoantibodies in schizophrenia

OBJECTIVE

Schizophrenia is associated with immune system dysfunction, including an increased prevalence of autoimmune disorders and autoantibodies. We performed a systematic, quantitative review of self-reacting blood antibodies in patients with schizophrenia.

METHOD

We identified articles by searching PubMed, PsychInfo, and ISI, and the reference lists of identified studies.

RESULTS

Eighty-one of 111 studies identified met the inclusion criteria. There was a significant increased prevalence of positive titers for 20 different autoantibodies in patients with schizophrenia compared to controls. The prevalence of positive anti-cardiolipin IgG and NMDA receptor titers was also significantly increased in subjects with first-episode psychosis versus controls (p<0.01). Absolute titers for anti-cardiolipin IgG and IgM, and nerve growth factor were significantly increased in patients with schizophrenia compared to controls (p<0.02 for each).

CONCLUSION

Schizophrenia is associated with an increased prevalence of multiple autoantibodies, although there is marked study heterogeneity, and correlations between autoantibodies and clinical features are inconsistent. This area merits more research evaluation, especially controlling for potential confounding factors such as clinical status, age, genetic background, psychotropic medications, BMI, and smoking.

Meta-analysis of lymphocytes in schizophrenia: clinical status and antipsychotic effects

BACKGROUND

Schizophrenia is associated with immune system dysfunction, including abnormal blood immune cell parameters. We performed a meta-analysis of these associations, considering the effect of clinical status and antipsychotic treatment following an acute exacerbation of psychosis.

METHODS

We identified articles by searching PubMed, PsycINFO, and Thomson Reuters (formerly ISI) Web of Knowledge and the reference lists of identified studies.

RESULTS

Sixteen studies of blood lymphocytes met the inclusion criteria. There was insufficient data for a meta-analysis of the mononuclear phagocytic system. In cross-sectional studies, there was a significant increase in the CD4% and CD56% in acutely relapsed inpatients. Absolute levels of total lymphocytes, CD3, and CD4, and the CD4/CD8 ratio were significantly increased, and the CD3% was significantly decreased in drug-native first-episode psychosis. In longitudinal studies, the CD4/CD8 ratio appeared to be state-related markers, as it decreased following antipsychotic treatment for acute exacerbations of psychosis. Absolute CD56 levels appeared to be a trait marker, as levels significantly increased following antipsychotic treatment for relapse.

CONCLUSIONS

Blood lymphocyte abnormalities in drug-naïve first-episode psychosis suggest an effect that may be independent of antipsychotic medications. While some parameters (CD4/CD8) may be state markers for acute exacerbations of psychosis, others (CD56) may be trait markers; however, more longitudinal studies are needed. Although these findings could provide the basis for future hypothesis testing, a relatively small number of studies and subjects, lack of correlative data with clinical features, and inadequate consideration of potential confounding factors limit the results.

Altered immune function in unaffected first-degree biological relatives of schizophrenia patients

Inflammatory and immune processes have been implicated in the etiopathology of schizophrenia. We demonstrate the existence of immune function alteration, assessed by serum cytokine's levels, not only in schizophrenia patients but also in their unaffected first-degree relatives. This finding may provide a new data for considering cytokines as schizophrenic disease biomarkers.

Impaired monocyte activation in schizophrenia

An inflammatory process is hypothesized in schizophrenia. Innate immunity, in particular the monocyte/macrophage system, has rarely been studied in this disorder, although alterations in microglia indicate a role for this system. Increased monocyte numbers have repeatedly been described. Toll-like receptors (TLRs) mediate the activation of monocytes. We studied the expression of the toll-like receptors TLR-2, TLR-3 and TLR-4 on CD14(+) monocytes in 31 schizophrenia patients and 31 sex- and age-matched healthy controls. Blood samples were taken and stimulated with either lipopolysaccharides (LPS), to mimic a bacterial infection, or polyI:C, to mimic a viral infection. Moreover, the intracellular concentration of interleukin-1ß (IL-1ß) in CD33(+) monocytes was estimated before and after stimulation. The intracellular concentrations of IL-1ß and the TLR surface markers were analyzed by flow cytometry. Receptor expression of TLR-3 and TLR-4, but not of TLR-2, was significantly higher in the schizophrenia patients. After stimulation, patients showed less increase in the expression of TLR-3 and TLR-4 than controls did. The IL-1ß concentration was significantly lower in patients both before and after stimulation with polyI:C, and there was a trend towards a lower concentration after LPS stimulation. The higher expression of TLR-3 and TLR-4 receptors might compensate for a functional deficit, and the lower intracellular concentrations of IL-1ß might reflect the blunted monocytic function in schizophrenia. The immunological dysfunctions might be associated with a poor clearance of pathogens in schizophrenia, which in turn could lead to a low-grade inflammatory process.

Dysregulation of chemo-cytokine production in schizophrenic patients versus healthy controls

Background

The exact cause of schizophrenia is not known, although several aetiological theories have been proposed for the disease, including developmental or neurodegenerative processes, neurotransmitter abnormalities, viral infection and immune dysfunction or autoimmune mechanisms. Growing evidence suggests that specific cytokines and chemokines play a role in signalling the brain to produce neurochemical, neuroendocrine, neuroimmune and behavioural changes. A relationship between inflammation and schizophrenia was supported by abnormal cytokines production, abnormal concentrations of cytokines and cytokine receptors in the blood and cerebrospinal fluid in schizophrenia. Since the neuropathology of schizophrenia has recently been reported to be closely associated with microglial activation we aimed to determined whether spontaneous or LPS-induced peripheral blood mononuclear cell chemokines and cytokines production is dysregulated in schizophrenic patients compared to healthy subjects. We enrolled 51 untreated first-episode schizophrenics (SC) and 40 healthy subjects (HC) and the levels of MCP-1, MIP-1α, IL-8, IL-18, IFN-γ and RANTES were determined by Elisa method in cell-free supernatants of PBMC cultures.

Results

In the simultaneous quantification we found significantly higher levels of constitutively and LPS-induced MCP-1, MIP-1α, IL-8 and IL-18, and lower RANTES and IFNγ levels released by PBMC of SC patients compared with HC. In ten SC patients receiving therapy with risperidone, olanzapine or clozapine basal and LPS-induced production of RANTES and IL-18 was increased, while both basal and LPS-induced MCP-1 production was decreased. No statistically significant differences were detected in serum levels after therapy.

Conclusion

The observation that in schizophrenic patients the PBMC production of selected chemo-cytokines is dysregulated reinforces the hypothesis that the peripheral cyto-chemokine network is involved in the pathophysiology of schizophrenia. These preliminary, but promising data are supportive of the application of wider profiling approaches to the identification of biomarker as diagnostic tools for the analysis of psychiatric diseases.

T- and B-lymphocytes in patients with schizophrenia in acute psychotic episode and the course of the treatment

Schizophrenia is associated with alterations of the immune system. There are, however, only limited data dealing with immune parameters in unmedicated schizophrenic patients and the course of these parameters during treatment. In this study, we monitored CD19+ (B)- and CD3+ (T)-lymphocytes in the course of antipsychotic treatment. Forty patients diagnosed with an acute exacerbation of schizophrenia were tested before and after 3 days, 2 weeks, 4 weeks and 3 months of treatment with antipsychotics. The percentages of CD19+- and CD3+ -lymphocytes were analysed by flow cytometry using fluorescence conjugated anti-CD19 and anti-CD3 antibodies. Twenty healthy volunteers served as controls. In the acute state of psychosis, a significant reduction of the CD3+ -lymphocyte subpopulation was observed, while the percentage of CD19(+)-lymphocytes was increased. Both subpopulations levelled to those of the control group in the course of treatment. As expected, the levels of the immune parameters did not change in the healthy controls during the course of the study. The observed alterations of the CD19+ - and CD3+ -lymphocytes in the acute state of psychosis especially in patients with the paranoid subtype of schizophrenia, and the "normalization" during the observation period are discussed under the aspect of the immune hypothesis of schizophrenia, in particular of the type-1/type-2 imbalance hypothesis.

Cytokines in schizophrenia and the effects of antipsychotic drugs

Growing evidence suggests that the immune, endocrine, and nervous systems interact with each other through cytokines, hormones, and neurotransmitters. The activation of the cytokine systems may be involved in the neuropathological changes occurring in the central nervous system (CNS) of schizophrenic patients. Numerous studies report that treatment with antipsychotic drugs affects the cytokine network. Hence, it is plausible that the influence of antipsychotics on the cytokine systems may be responsible for their clinical efficacy in schizophrenia. This article reviews current data on the cytokine-modulating potential of antipsychotic drugs. First, basic information on the cytokine networks with special reference to their role in the CNS as well as an up-to-date knowledge of the cytokine alterations in schizophrenia is outlined. Second, the hitherto published studies on the influence of antipsychotics on the cytokine system are reviewed. Third, the possible mechanisms underlying antipsychotics' potential to influence the cytokine networks and the most relevant aspects of this activity are discussed. Finally, limitations of the presented studies and prospects of future research are delineated.

Monocyte chemoattractant protein-1 promoter -2518 polymorphism and schizophrenia in the Korean population

The purpose of the present study was to investigate the association between the monocyte chemoattractant protein-1 (MCP-1) promoter -2518 polymorphism and schizophrenia. One hundred and twenty-three schizophrenic inpatients and 114 healthy controls participated in this study. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism. Genotype and allele distributions in patients with schizophrenia were not significantly different from those of the controls. However, distributions of genotypes and alleles were marginally different when considering subjects with positive and negative symptomatology. The present study therefore calls for further studies on the potential role of the MCP-1 promoter -2518 polymorphism in clinical heterogeneity of schizophrenia.

Search for atypical lymphocytes in schizophrenia

The existence of atypical lymphocytes with specific morphological characteristics in the peripheral blood of schizophrenic patients has been suggested in several reports over the last 40 years. In our study this observation was examined not only by using the formerly applied method of light microscopy for general cell distribution and lymphocyte morphology but also by applying flow cytometry, a well established immunological method for lymphocyte patterns such as lymphocyte subgroups and lymphocyte activity. In contrast to the previously published data, our results demonstrated no differences in cell distribution (lymphocytes, polymorphonuclear cells, eosinophil and basophil granulocytes, monocytes), lymphocyte morphology ("atypical lymphocytes" vs. "normal lymphocytes"), distribution of lymphocyte-subtypes (T-cells (CD3(+)), T-helper-cells (CD3(+)/CD4(+)), cytotoxic T-cells (CD3(+)/CD8(+)), B-cells (CD19(+)), NK-cells (CD3(-)/CD56(+))) or state of T-lymphocyte activity (CD25(+) or HLA-DR(+)-cells) in schizophrenic patients compared to healthy controls. We suggest that possible immunological alterations in schizophrenia do not correlate with morphological characteristics of lymphocytes observable by light microscopy or an altered state activity of T-lymphocytes examined by flow cytometric parameters. Further studies should concentrate on intracellular and functional aspects of the different lymphocyte subgroups.

Immunity and schizophrenia: autoimmunity, cytokines, and immune responses

As is evident from the present account, there is no single or persuasive argument that signals emanating from the immune system are directly involved in the etiology of schizophrenia. We do not even know if we are dealing with a single disorder with a single causality; almost certainly we are not. The precise etiology of schizophrenia, as with so many neurological disorders, remains obscure. However, there is abundant evidence in schizophrenia of mutual dysregulation of neuronal function and immune system activity. Although this evidence is not always consistent, a pattern emerges suggesting aspects of immune activity being involved in the pathology of neuronal development that characterizes schizophrenia. Exposure to infective agents, HLA associations, autoimmune associations, disturbances in lymphocyte populations, and cytokine imbalances with a skew toward Th2 activity are supportive of this view. That the evidence is not always consistent is a testament to the complexity and heterogeneity of the disorder, to confounding by antipsychotics that themselves are immunomodulatory, and to the multifaceted nature, with all its checks and balances, of the immune system itself.

Review of immunological and immunopathological findings in schizophrenia

The involvement of immunological and immunopathological mechanisms in the etiopathogenesis of schizophrenia has been a matter of research, with recently increasing effort. This article reviews the findings focusing on postmortem neuropathology, the blood-brain barrier, antibodies, acute phase proteins, immunocompetent cells, and activation markers of immunocompetent cells. Evidence for the two primarily postulated hypotheses (the infectious hypothesis and the autoimmune hypothesis) is critically discussed. On the basis of the findings, perspectives for future research are outlined aiming at a precise and consequent strategy to elucidate a potential involvement of immune mechanisms in the etiopathogenesis of schizophrenia.

In vitro cytokine secretion in individuals with schizophrenia: results, confounding factors, and implications for further research

The present paper reviews the results of all publications on in vitro cytokine secretion in patients with schizophrenia, as published by March 2001. The authors supply easy to read tables with respect to the individual cytokines and soluble cytokine receptors investigated, the in vitro methodology used, characterization of the patient samples, and the results on cytokine secretion as stated in these studies. Inconsistent results, e.g., regarding in vitro secretion of IL-2 with 11/18 studies finding decreased secretion, 5/18 finding no change, and 2/18 finding increases, cannot systematically be correlated with any methodological procedures nor any diagnostic subtypes, per se. However, factors such as medication and cigarette smoking are likely to play a role. The authors suggest that more hypothesis-driven research, together with more carefully designed studies, as well as better communication between basic or animal researchers and clinicians might help to answer the question of whether there are meaningful peripheral changes in the immune system related to schizophrenia.

T-helper-1 and T-helper-2 responses in psychiatric disorders

The expanding field of psychoneuroimmunology has markedly increased knowledge about the interference of the central nervous system and the immune system. Immunological abnormalities in psychiatric patients have been repeatedly described in the last century. Modern concepts of immunology and the growing knowledge of psychoneuroimmunology may help in understanding the distinct immunological mechanisms in psychiatric disorders. One of these concepts regarding the adaptive immune system is the discrimination between Th1-like cell-mediated and Th2-like antibody-related immune responses. This article systematically describes alterations of Th1- or Th2-specific parameters in the major psychiatric disorders schizophrenia, major depression, and Alzheimer's disease. There are several hints of associations of these two distinct arms of immune response with subgroups of schizophrenia and major depression. The immunological research in Alzheimer's disease has already led to a preclinical model of immunotherapy. Categorization of immune parameters may also help to identify a possible immune-related pathophysiology in psychotic and affective disorders, resulting in specific treatment strategies.

The Th2-hypothesis of schizophrenia: a strategy to identify a subgroup of schizophrenia caused by immune mechanisms

Immunologic findings in schizophrenia have been described for decades, but it was not possible to identify a pathogen until now. Most of these studies report immune abnormalities in a group of the investigated patients, but a distinct subgroup of schizophrenia with immune-related pathology has still not been characterized. In this paper we have integrated the most important immunologic data in schizophrenia research and hypothesize a shift to Th2-like immune reactivity in a subgroup of schizophrenic patients. Besides the immunological abnormalities, this subgroup is further characterized by more pronounced negative symptoms and poor therapy outcome. There is evidence that this subgroup might be caused by a prenatal viral infection.

Effects of atypical antipsychotics on the inflammatory response system in schizophrenic patients resistant to treatment with typical neuroleptics

There is now some evidence that schizophrenia may be accompanied by an activation of the inflammatory response system (IRS) and that typical antipsychotics may suppress some signs of IRS activation in that illness. This study was carried out to examine (i) the serum concentrations of interleukin-6 (IL-6), IL-6 receptor (IL-6R), IL-1R antagonist (IL-1RA) and Clara Cell protein (CC16), an endogenous anticytokine, in nonresponders to treatment with typical neuroleptics and (ii) the effects of atypical antipsychotics on the above IRS variables. The above parameters were determined in 17 patients with treatment-resistant schizophrenia (TRS) to treatment with neuroleptics and in seven normal volunteers and 14 schizophrenic patients who had a good response to treatment with antipsychotic agents. Patients with TRS had repeated measurements of the IRS variables before and 2 and 4 months after treatment with atypical antipsychotics. Serum IL-6 was significantly higher in schizophrenic patients, irrespective of their response to typical antipsychotics, than in normal controls. Serum IL-1RA was significantly higher in the TRS patients than in controls, whereas responders took up an intermediate position. The serum concentrations of CC16 were significantly lower after treatment with atypical antipsychotics during 4 months than before treatment. It is concluded that (i) schizophrenia and, in particular, TRS is characterized by an activation of the monocytic arm of cell-mediated immunity and (ii) atypical antipsychotics may decrease the anti-inflammatory capacity of the serum in TRS patients.

Decreased in vitro production of interferon-gamma and interleukin-2 in whole blood of patients with schizophrenia during treatment

A pattern of aberrations in the T-cell cytokine system that is typical for autoimmune disorders has also been reported in patients with schizophrenia, namely a decreased interleukin-2 (IL-2) production and increased levels of the soluble IL-2 receptor (sIL-2R). It has also been reported that the production of interferon-gamma (IFN-gamma) may be lowered. In a longitudinal design, we studied the production of both IFN-gamma and IL-2 and their correlation in patients with schizophrenia during treatment and investigated whether associations exist between cytokine production and clinical variables. The production of IFN-gamma and IL-2 was measured in equal numbers (n = 29) of patients with schizophrenia (DSM-IV) and controls who were matched for age and gender. Patients were measured 1 day after admission (T1), after 14 (T2) and 28 (T2) days of treatment. Psychopathology was assessed after these times. The production of both IFN-gamma and IL-2 was significantly lower in patients than in controls throughout the whole investigation period (T1-T3). The productions of both cytokines were significantly correlated in controls (r = 0.60, P </= 0.001) as well as in patients with schizophrenia (mean production T1-T3: r = 0.71, P </= 0.001). No associations between cytokine measurements and psychopathology or age-at-onset could be found. Our findings of lowered and correlated IFN-gamma and IL-2 production indicate that alterations in the cytokine system of patients with schizophrenia might resemble those in autoimmune disorders. It is suggested that these immunological abnormalities are associated with acute exacerbation, rather than with a clinical subtype of schizophrenia.

Dopamine, a neurotransmitter, influences the immune system

Dopamine (DA) is a monoamine neurotransmitter of both central and peripheral nervous system. Its role in the neural-immune communication has been discussed in the present review. Results reveal that in vivo damage or stimulation of specific central dopaminergic system suppresses or enhances functional activities of the immune effector cells. The possible influences of other immunomodulators of the brain by altering brain DA may be the underlying mechanism. Direct effects of DA on the immune effector cells are also contradictory, it is suppressive in vitro, while in pharmacological doses, it is mostly stimulatory in vivo. The possible mechanisms have been discussed. Lastly, future areas of relevance on DA and immunity have been highlighted to advance our knowledge regarding DA as an immune regulator.

Increased serum neopterin levels in acutely ill and recovered schizophrenic patients

Twenty-nine in-patients with acute schizophrenia were examined to assess serum neopterin levels by ELISA at two points of time: during the state of acute symptoms and after clinical recovery at the point of discharge (at an interval of 30.84 +/- 15.22 days). Patients showed significantly higher levels of neopterin than controls. Moreover, the neopterin levels were significantly higher in patients after clinical improvement than in acutely ill patients. Neopterin levels in patients after clinical recovery were negatively correlated to scores of psychopathological symptoms, and positively to neuroleptic medication at the acute stage of the disease. The increase of serum neopterin during treatment of schizophrenia may reflect an up-regulation of dopamine turnover, rather than immunological activity.