Increased serum IgE in schizophrenic patients who responded poorly to neuroleptic treatment

Comparison of peripheral and central schizophrenia biomarker profiles

We have recently shown that a molecular biomarker signature comprised of inflammatory, hormonal and growth factors occurs in the blood serum from first onset schizophrenia patients. Here, we use the same platform to investigate post mortem brain tissue (Brodmann area 10) from schizophrenia patients who were mainly chronically ill and drug treated. Twenty-one analytes are differentially expressed in post-mortem brain tissue. Comparison with our previous mRNA profiling studies of the same patient samples in another frontal cortical area showed that 9 of these molecules were also altered at the transcriptional level. Furthermore, 9 of the molecules were also altered in serum from living first onset schizophrenia patients compared to controls. We propose a model in which the brain and periphery are coordinated through hormones and other regulatory molecules released into the blood via the diffuse neuroendocrine system. These findings provide further evidence for the systemic nature of schizophrenia and give added validity to the concept that schizophrenia can be investigated through studies of blood-based biomarkers.

Neuroimmune pharmacology of neurodegenerative and mental diseases

Neuroimmune pharmacology is a newly emerging field that intersects with neuroscience, immunology, and pharmacology and that is seeking avenues for translational research and better understanding of disease mechanisms. It focuses on the immunity of the central nervous system (CNS) which is greatly influenced by endogenous effectors, such as cytokines and neurotransmitters, and by exogenous substances, including therapeutic compounds, infectious pathogens, and drugs of abuse. In this article, we attempt to raise awareness of the pivotal discovery of how those mediators affect the immunity of the CNS in both physiological conditions and processes of certain mental illnesses, including psychiatric disorders, neurodegenerative diseases, and cerebral dysfunctions due to drugs of abuse. The abnormality in cytokine networks, neurotransmitter homeostasis, and other immune responses may be involved in the neuropathology associated with those mental illnesses, and the therapeutic effects of the potential treatments can be attributed, at least partially, to their immunomodulatory activities. However, the resulting inflammatory cytokines from certain treatments frequently cause psychiatric complications. In addition, the poor neuropathological outcomes frequently found among drug abusers with HIV-1 infection appear to be related to the neurotoxic and immunomodulatory effects of the drugs used. Importantly, glial cells, especially microglia and astrocytes, are key players in the immunomodulatory activities in the CNS, and the functioning CNS is largely dependent upon the reciprocal interactions between neurons and glial cells. Therefore, glia-neuron interactions have become a critical issue for further understanding the disease mechanism. From this review, readers will gain insights into the new field of neuroimmune pharmacology, with a focus on the impacts of CNS immunity on the mental illnesses.

Allelic frequencies of 3' Ig heavy chain locus enhancer HS1,2-A associated with Ig levels in patients with schizophrenia

Infectious and autoimmune pathogenic hypotheses of schizophrenia have been proposed, prompting searches for antibodies against viruses or brain structures, and for altered levels of immunoglobulins. Previous experiments have shown that allele frequencies of the Ig heavy chain 3' enhancer HS1,2*A are associated with several autoimmune diseases, suggesting a possible correlation between HS1,2 alleles and Ig production. To test this, we analyzed levels of serum Igs and HS1,2*A genotypes in two independent cohorts, one of 88 schizophrenic inpatients (24 women) and a second of 133 healthy subjects (59 women). Both groups were similar in the frequency of individuals with altered serum concentration of Ig classes and IgG subclasses (schizophrenia panel-80 percent; controls-68 percent). With the possible exception of a stabilizing effect of olanzapine, no psychopharmacological drug consumed during the month prior to serum sampling in the schizophrenia group significantly affected Ig levels. In both patient and control cohorts, an increased frequency of the HS1,2*2A allele corresponded to increased Ig plasma levels, while an increased frequency of the HS1,2*1A allele corresponded to decreased Ig plasma levels. EMSA analysis with nuclear extracts from human B cells showed that the transcription factor SP1 bound to the polymorphic region of both HS1,2*1A and HS1,2*2A while NF-kB bound only to the HS1,2*2A. We predict that differences in transcription factor binding sites in the two allelic variants of the 3' IgH enhancer HS1,2 may provide a mechanism by which differences in Ig expression are affected.

Association study of interleukin 2 (IL2) and IL4 with schizophrenia in a Japanese population

Interleukin 2 (IL-2) and IL-4 are pleiotropic cytokines regulating Th1/Th2 balance and have a regulatory activity in brain function. Thus these cytokines have been implicated in the pathophysiology of schizophrenia. The latest studies provided controversial results regarding the genetic associations of these cytokines. The functional polymorphisms, IL2-330T/G and IL4-590C/T, were associated with schizophrenia in a German population, although contradictory findings were also reported in a Korean population. To ascertain whether IL2 and IL4 contribute to vulnerability to schizophrenia, we conducted a moderate-scale case-control (536 patients and 510 controls) association study for seven polymorphisms in Japanese subjects. There were no significant associations of these genes with schizophrenia using either single marker or haplotype analyses. The present study suggests that IL2 and IL4 do not contribute to vulnerability to schizophrenia in the Japanese population.

Problems and promise of immunological factors as biomarkers for schizophrenia

The complex and multifactorial etiology of psychiatric disorders, and in particular that of schizophrenia, has made it difficult to identify biomarkers suitable for clinical diagnosis. In schizophrenia research, the investigation of immune-related factors has been of central importance in the quest to unravel the disease etiology. However, immunological findings have been controversial, and the importance of an underlying immunopathology in schizophrenia remains to be irrevocably established. Here we review those findings that have been most consistently reported. We further address their potential utility for clinical diagnosis and drug development. We also discuss problems connected to sample collection and preparation, with special focus on their effects on immune-derived parameters. In light of recent findings, we highlight the potential of combining functional cell-based assays with high-throughput multiomics experiments for the discovery of novel biomarkers.

[Immunology in schizophrenic disorders]

This manuscript deals with whether immune-mediated mechanisms of inflammation contribute to the pathogenesis of schizophrenia. A model is presented which integrates psychoneuroimmunologic findings and actual results from pharmacological, neurochemical, and genetic studies in schizophrenia. A pivotal role in the neurobiology of schizophrenia is played by dopaminergic neurotransmission, which is modulated by influences of the glutamatergic system. The decreased function of the glutamate system described in schizophrenia seems primarily mediated by N-methyl-D-aspartate (NMDA) receptor antagonism. Kynurenine acid is the only known endogenous NMDA receptor antagonist. In higher concentrations it blocks the NMDA receptor, but in lower concentrations it blocks the nicotinergic acetylcholin receptor, which has a prominent role in cognitive functions. Therefore, higher levels of kynurenine acid may explain psychotic symptoms and cognitive dysfunction. Several findings point out that prenatal infection, associated with an early sensitisation of the immune system, may result in an imbalance of the immune response (type 1 vs type 2) in schizophrenia. This immune constellation leads to inhibition of the enzyme indoleamin dioxigenase (IDO). It and tryptophane 2,3-dioxygenase (TDO) both catalyse the degradation from tryptophan to kynurenine. Due to the inhibition of IDO, tryptophan is metabolised to kynurenine primarily by TDO. In the CNS, TDO is located only in astrocytes, which are in particular activated in schizophrenia and in which kynurenine acid is the final product and can not be further metabolised. Therefore kynurenine acid accumulates in the CNS of schizophrenics and - due to its NMDA-antagonistic properties - leads to cognitive dysfunction and psychotic symptoms. This model describes the pathway of immune-mediated glutamatergic-dopaminergic dysregulation, which may lead to the clinical symptoms of schizophrenia. Therapeutic consequences (e.g. cyclo-oxygenase-2 inhibitors) are discussed.

Schizophrenia as an inflammation-mediated dysbalance of glutamatergic neurotransmission

This overview tries to bridge the gap between psychoneuroimmunological findings and recent results from pharmacological, neurochemical and genetic studies in schizophrenia. Schizophrenia is a disorder of dopaminergic neurotransmission, but modulation of the dopaminergic system by glutamatergic neurotransmission seems to play a key role. This view is supported by genetic findings of the neuregulin- and dysbindin genes, which have functional impact on the glutamatergic system. Glutamatergic hypofunction, however, is mediated by the N-methyl-D-aspartate (NMDA)-receptor antagonism. The only endogenous NMDA receptor antagonist identified up to now is kynurenic acid (KYNA). Despite the NMDA receptor antagonism, KYNA also blocks, in lower doses, the nicotinergic acetycholine receptor, i.e., increased KYNA levels can explain psychotic symptoms and cognitive deterioration. KYNA levels are described to be higher in the cerebrospinal fluid (CSF) and in critical central nervous system (CNS) regions of schizophrenics as compared to controls. Another line of evidence suggests that a (prenatal) infection is involved in the pathogenesis of schizophrenia. Due to an early sensitization process of the immune system or to a (chronic) infection, which is not cleared through the immune response, an immune imbalance between the type-1 and the type-2 immune responses takes place in schizophrenia. The type-1 response is partially inhibited, while the type-2 response is over-activated. This immune constellation is associated with inhibition of the enzyme indoleamine dioxygenase (IDO), because IDO - located in astrocytes and microglial cells - is inhibited by type-2 cytokines. IDO catalyzes the first step in tryptophan metabolism, the degradation from tryptophan to kynurenine, as does tryptophan 2,3-dioxygenase (TDO). Due to the inhibition of IDO, tryptophan-kynurenine is predominantly metabolized by TDO, which is located in astrocytes, not in microglial or other CNS cells. In schizophrenia, astrocytes in particular are activated, as increased levels of S100B appear. Additionally, they do not have the enzymatic equipment for the normal metabolism-route of tryptophan. Due to the lack of kynurenine hydroxylase (KYN-OHase) in astrocytes, KYNA accumulates in the CNS, while the metabolic pathway in microglial cells is blocked. Accordingly, an increase of TDO activity has been observed in critical CNS regions of schizophrenics. These mechanisms result in an accumulation of KYNA in critical CNS regions. Thus, the immune-mediated glutamatergic-dopaminergic dysregulation may lead to the clinical symptoms of schizophrenia. Therapeutic consequences, e.g., the use of anti-inflammatory cyclo-oxygenase-2 inhibitors, which can also decrease KYNA directly, are discussed.

Lymphocytes as a neural probe: potential for studying psychiatric disorders

There is an increasing body evidence pointing to a close integration between the central nervous system (CNS) and immunological functions with lymphocytes playing therein a central role. The authors provide arguments to consider blood lymphocytes as a convenient probe of--an albeit--limited number of cellular functions, including gene expression. The use of brain biopsies of living patients is unrealistic for biochemical investigation, therefore lymphocytes may be a convenient and accessible alternative. Numerous studies showed similarities between receptor expression and mechanisms of transduction processes of cells in the nervous system (e.g. neurons and glia) and lymphocytes. In several neuropsychiatric disorders, alteration of metabolism and cellular functions in the CNS, as well as disturbances in the main neurotransmitter and hormonal systems are concomitant with altered function and metabolism of blood lymphocytes. We summarize relevant investigations on depression, stress, Alzheimer's disease (AD) and schizophrenia. New techniques such as cDNA microarray gene expression and proteomics may give clues to define molecular abnormalities in psychiatric disorders and could eventually reveal information for diagnostic and treatment purposes. Taken together, these considerations suggest that lymphocyte could reflect the metabolism of brain cells, and may be exploited as a neural and possible genetic probe in studies of psychiatric disorders.

Autoantibodies against four kinds of neurotransmitter receptors in psychiatric disorders

There is a hypothesis that autoimmune abnormalities in neurotransmitter receptors might cause some psychiatric disorders. Using a sensitive radioligand assay, we detected serum autoantibodies to recombinant human muscarinic cholinergic receptor 1 (CHRM1, 34.4%), mu-opioid receptor (OPRM1, 13.1%), 5-hydroxytryptamine receptor 1A (HTR1A, 7.4%), and dopamine receptor D2 (DRD2, 4.9%) in 122 psychiatric patients. Positive antibodies to CHRM1 were found in 34.1%, 34.9%, 33.3%, and 9.1% of patients with schizophrenic disorders (n=44), mood disorders (n=63), other psychiatric disorders (n=15) and autoimmune diseases (n=33), respectively. All three patients with neuroleptic maliganant syndrome had high activities of autoantibodies to CHRM1, OPRM1, and/or HTR1A. Our data suggest that autoimmunity to neurotransmitter receptors might be associated with the induction of psychiatric symptoms and have some relation to neuroleptic malignant syndrome.

Polymorphisms of interleukin-4 promoter and receptor gene for schizophrenia in the Korean population

The purpose of the present paper was to investigate the interleukin (IL)-4 promoter gene -590 and receptor alpha (Ralpha) gene 1902 polymorphism in Korean schizophrenic patients. A total of 222 Korean patients diagnosed with schizophrenia according to Diagnostic and Statistical Manual of Mental Disorders (4th edn; DSM-IV) and 165 normal healthy controls participated in the present study. The DNA was extracted from whole blood using proteinase K, and the IL-4 promoter and receptor gene were amplified by polymerase chain reaction. The genotype was determined using single-strand conformation polymorphism (SSCP) analysis. The distribution of the alleles and genotypes in patients with schizophrenia was not significantly different from those of controls. In conclusion, these results suggest that the polymorphisms in IL-4 promoter gene -590 and IL-4 Ralpha gene 1902 are not involved in the pathophysiology of schizophrenia in the Korean population.

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.

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 immune system and schizophrenia. An integrative view

Immune alterations in schizophrenia have been described for decades. Modern immunological methods and new insights into the highly developed and functionally differentiated immune system allow an integrative view of both the older and the recent findings of immunological abnormalities in schizophrenia. Both the unspecific and the specific arms of the immune system seem to be involved in the dysfunction of the immune system in schizophrenia. The unspecific, "innate" immune system shows signs of overactivation in unmedicated schizophrenic patients, as indicated by increased monocytes and gamma delta-cells. Increased levels of interleukin-6 (IL-6) and the activation of the IL-6 system in schizophrenia might be the result of the activation of monocytes/macrophages, too. On the other hand, several parameters of the specific cellular immune system are blunted, such as, for example, the decreased T helper-1 (TH-1)-related immune parameters in schizophrenic patients both in vitro and in vivo. It seems that a TH-1-TH-2 imbalance with a shift to the TH-2 system is associated with schizophrenia. During antipsychotic therapy with neuroleptics, the specific TH-1-related immune answer becomes activated, but in addition the B cell system and antibody production increase.

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.

Cellular and humoral immune system in schizophrenia: a conceptual re-evaluation

Immune alterations in schizophrenia have been described for decades. However, modern immunological methods and new insights into the highly developed and functionally differentiated immune system allow an integrative view of both the older and also more recent findings of immunological abnormalities in schizophrenia. The conceptual advances in immunology require the re-evaluation of elder immunological findings in schizophrenia. In this overview, recent advances in immunological research regarding the differentiation between T-Helper-1 and T-Helper-2 cells and between the so-called specific and unspecific arms of the immune system are discussed. The unspecific "innate" immune system shows signs of an over-activation in unmedicated schizophrenic patients, as increased monocytes and gamma delta-cells point to. Increased levels of Interleukin-6 (IL-6) and the activation of the IL-6 system in schizophrenia might be the result of the activation of monocytes/macrophages, too. In contrast, several parameters of the specific cellular immune system are blunted, e.g. the decreased T-helper-1 (TH-1) related immune parameters in schizophrenic patients, both in vitro and in vivo. It seems that a TH-1-TH-2 imbalance with a shift to the TH-2 system is associated with schizophrenia. During therapy with antipsychotics, the specific TH-1 related immune answer becomes activated, but the B-cell system and the antibody production become activated too.

Decreased levels of soluble intercellular adhesion molecule-1 (sICAM-1) in unmedicated and medicated schizophrenic patients

BACKGROUND

The soluble intercellular adhesion molecule-1 (sICAM-1) is a marker for the activation of the cellular immune system. Since an activation of the immune system has been observed in a part of the schizophrenic patients, we measured the serum levels of soluble ICAM-1 (sICAM-1) in schizophrenic patients and correlated them to the patient's psychopathology.

METHODS

To monitor a possible effect of antipsychotic therapy, 36 schizophrenic patients were examined twice: first without antipsychotic medication immediately after admission to the hospital and then, after clinical improvement before discharge. The results were compared with those of 36 age- and gender-related healthy individuals.

RESULTS

The schizophrenic patients showed significantly decreased serum levels of sICAM-1 at the first examination (248 +/- 95 ng/mL) and at re-examination (266 +/- 95 ng/mL) compared with the comparison group (323 +/- 74 ng/mL). Patients with more pronounced negative symptoms showed higher levels of sICAM-1 at the first examination.

CONCLUSIONS

We conclude that reduced sICAM-1 levels in schizophrenia indicate a reduced activity of the cellular immune system in at least a subgroup of schizophrenic patients.

The relationship between serum concentration and therapeutic effect of haloperidol in patients with acute schizophrenia

Haloperidol is the most commonly used antipsychotic drug in the therapy of acute schizophrenia. Clinicians have been using therapeutic drug monitoring in an attempt to improve clinical application of this drug. The scale of interest in this area is emphasised by the large number of studies (about 50) concerning the serum concentration-therapeutic effect relationship (SCTER) of haloperidol, including 35 studies on patients with acute schizophrenia. However, conflicting results concerning the existence and position of a therapeutic window have emerged. This article aims to provide a comprehensive review of the study design of studies in patients with acute schizophrenia before the study data are used for decision-making. For this purpose, a reproducible system for the evaluation of studies in this special area, a so-called total study score (TSS), was developed on an empirical basis. Thus, insufficient study design was found to be a reason for negative results. On the other hand, in spite of a great variability, the majority of studies with good design provided evidence for a significant SCTER: a bisigmoidal dependence of clinical effect on haloperidol serum concentration. The therapeutic effects of haloperidol increase at low concentrations, and the concentration has a maximum effect at about 10 micrograms/L and again decreasing at higher concentrations. The data of 552 patients also fit to this model in a single scatter plot (pseudo-r2 = 0.076, p < 0.001). The position of the therapeutic window was determined at about 5.6 to 16.9 micrograms/L. Patients treated with serum concentrations within this optimal range had a significantly better response compared with outside this range (p < 0.001, Student t-test). Therefore, a quantitative synthesis of all available data by means of effect-size analysis provides a mean effect-size (g) = 0.499 +/- 0.182 (standard deviation) for the comparison of haloperidol-treatment with serum concentrations within versus outside the therapeutic window. Thus, because of this moderate positive effect, serum concentration assay of haloperidol is recommended for patients with acute schizophrenia in a therapeutic drug monitoring programme. The modalities of haloperidol therapeutic drug monitoring in clinical practice are discussed, e.g. patient selection, method and time for serum concentration measurement, influence of premedication and comedication, interpretation of results and dose adjustment. Clinical investigations into this subject should focus on covariates which are responsible for the variability of the SCTER. Serum concentration assay is advised for investigations of nonresponse to exclude patients with pseudo-drug resistance.

Increased allergic reactivity of atopic type in mood disorders and schizophrenia

The allergic reactivity of atopic type was investigated in 54 patients with mood disorders in the course of depressive episode and in 39 patients with schizophrenia. The assessment was done by three methods: intradermal tests, determination of IgE concentration and determination of specific immunoglobulin E (IgE) antibodies. The hypersensitivity to three or more allergens on intradermal tests was found in 40% of depressive and in 27% of schizophrenic patients. The concentration of IgE > 100 IU/mL was found in 45% of patients with depression and in 46% of patients with schizophrenia, more frequently in subjects with hyperactivity of hypothalamic-pituitary-adrenal axis, and in depression, in patients with higher intensity of symptoms. The positive results of the Phadiatop test which detects specific antibodies for inhalatory antigens, were found in 46% of depressive and in 40% of schizophrenic patients The indices of atopy for all three tests were higher in males than in females in both mood disorders and in schizophrenia. However, these indices were similar for unipolar and bipolar depressed patients as well as for patients with paranoid or residual schizophrenia.