Altered interleukin-2 production in schizophrenia: association between clinical state and autoantibody production

Prevalence of Anti-Nuclear Antibodies and Anti-Phospholipid Antibodies in an Egyptian Cohort with Schizophrenia: A Case-Control Study

BACKGROUND

Psychiatric disorders, including schizophrenia could herald other manifestation(s) of systemic lupus erythematosus (SLE) potentially hindering timely and optimal management. Moreover, schizophrenia is among the described 'extra-criteria' manifestations of anti-phospholipid syndrome (APS). Hence, screening schizophrenia patients for SLE and APS may pose diagnostic and therapeutic implications.

OBJECTIVES

Examine schizophrenia patients with no overt connective tissue disease(s) manifestation(s) for clinical and/or serologic evidence of SLE and/or APS.

METHODS

The study included 92 schizophrenia patients [61 (66.3%) males] and 100 age- and gender-matched healthy controls. Both groups were tested for anti-nuclear antibodies (ANAs), anti-double stranded deoxyribonucleic acid (anti-dsDNA) antibodies, complement 3 (C3) and C4, and criteria anti-phospholipid antibodies (aPL) [anticardiolipin Immunoglobulin (Ig) G and IgM, anti-beta-2-glycoprotein I IgG and IgM, and lupus anticoagulant (LAC)].

RESULTS

The patients' mean age and disease duration were 28.8 ± 8.1 and 5.7 ± 2.2 years, respectively. The prevalence of ANA positivity, height of titre, and pattern was comparable between patients and controls (p = 0.9, p = 0.8 and p = 0.1, respectively). Anti-dsDNA antibodies and hypocomplementemia were absent in both groups. A significantly higher frequency of positive LAC was observed among patients compared with controls (7.6 % vs. 1 %, p = 0.02), whereas other aPL were comparable between both groups. None of the patients or controls demonstrated clinically meaningful (medium or high) aPL titres.

CONCLUSION

In our study, schizophrenia was solely associated with LAC. Thus, in the absence of findings suggestive of SLE or APS, routine screening for both diseases is questionable.

Therapeutic Drug Monitoring of Second- and Third-Generation Antipsychotic Drugs-Influence of Smoking Behavior and Inflammation on Pharmacokinetics

Both inflammation and smoking can influence a drug’s pharmacokinetic properties, i.e., its liberation, absorption, distribution, metabolism, and elimination. Depending on, e.g., pharmacogenetics, these changes may alter treatment response or cause serious adverse drug reactions and are thus of clinical relevance. Antipsychotic drugs, used in the treatment of psychosis and schizophrenia, should be closely monitored due to multiple factors (e.g., the narrow therapeutic window of certain psychotropic drugs, the chronicity of most mental illnesses, and the common occurrence of polypharmacotherapy in psychiatry). Therapeutic drug monitoring (TDM) aids with drug titration by enabling the quantification of patients’ drug levels. Recommendations on the use of TDM during treatment with psychotropic drugs are presented in the Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology; however, data on antipsychotic drug levels during inflammation or after changes in smoking behavior—both clinically relevant in psychiatry—that can aid clinical decision making are sparse. The following narrative review provides an overview of relevant literature regarding TDM in psychiatry, particularly in the context of second- and third-generation antipsychotic drugs, inflammation, and smoking behavior. It aims to spread awareness regarding TDM (most pronouncedly of clozapine and olanzapine) as a tool to optimize drug safety and provide patient-tailored treatment.

Therapeutic Drug Monitoring of Second- and Third-Generation Antipsychotic Drugs—Influence of Smoking Behavior and Inflammation on Pharmacokinetics

Both inflammation and smoking can influence a drug’s pharmacokinetic properties, i.e., its liberation, absorption, distribution, metabolism, and elimination. Depending on, e.g., pharmacogenetics, these changes may alter treatment response or cause serious adverse drug reactions and are thus of clinical relevance. Antipsychotic drugs, used in the treatment of psychosis and schizophrenia, should be closely monitored due to multiple factors (e.g., the narrow therapeutic window of certain psychotropic drugs, the chronicity of most mental illnesses, and the common occurrence of polypharmacotherapy in psychiatry). Therapeutic drug monitoring (TDM) aids with drug titration by enabling the quantification of patients’ drug levels. Recommendations on the use of TDM during treatment with psychotropic drugs are presented in the Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology; however, data on antipsychotic drug levels during inflammation or after changes in smoking behavior—both clinically relevant in psychiatry—that can aid clinical decision making are sparse. The following narrative review provides an overview of relevant literature regarding TDM in psychiatry, particularly in the context of second- and third-generation antipsychotic drugs, inflammation, and smoking behavior. It aims to spread awareness regarding TDM (most pronouncedly of clozapine and olanzapine) as a tool to optimize drug safety and provide patient-tailored treatment.

Therapeutic Drug Monitoring of Second- and Third-Generation Antipsychotic Drugs-Influence of Smoking Behavior and Inflammation on Pharmacokinetics

Both inflammation and smoking can influence a drug's pharmacokinetic properties, i.e., its liberation, absorption, distribution, metabolism, and elimination. Depending on, e.g., pharmacogenetics, these changes may alter treatment response or cause serious adverse drug reactions and are thus of clinical relevance. Antipsychotic drugs, used in the treatment of psychosis and schizophrenia, should be closely monitored due to multiple factors (e.g., the narrow therapeutic window of certain psychotropic drugs, the chronicity of most mental illnesses, and the common occurrence of polypharmacotherapy in psychiatry). Therapeutic drug monitoring (TDM) aids with drug titration by enabling the quantification of patients' drug levels. Recommendations on the use of TDM during treatment with psychotropic drugs are presented in the Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology; however, data on antipsychotic drug levels during inflammation or after changes in smoking behavior-both clinically relevant in psychiatry-that can aid clinical decision making are sparse. The following narrative review provides an overview of relevant literature regarding TDM in psychiatry, particularly in the context of second- and third-generation antipsychotic drugs, inflammation, and smoking behavior. It aims to spread awareness regarding TDM (most pronouncedly of clozapine and olanzapine) as a tool to optimize drug safety and provide patient-tailored treatment.

Inflammatory cytokine network in schizophrenia

OBJECTIVES

The purpose of this review is to analyse, sum up and discuss the available literature on the role of inflammation and inflammatory cytokines in the pathogenesis of schizophrenia.

METHODS

An electronic literature search of peer-reviewed English language articles using Pubmed was undertaken. These articles together with those published by us provided the background for the present review.

RESULTS

An overview of the available literature on this issue clearly demonstrated the alterations in mRNA and protein expression levels of several proinflammatory and chemotactic cytokines in patients with schizophrenia. Importantly, some of these changes are genetically determined. It was noteworthy that, depending on the study population, some variations of the data obtained are detected.

CONCLUSIONS

Altered inflammatory cytokine production, both genetically and environmentally determined, is implicated in schizophrenia and contributes to disease-associated low-grade systemic inflammation. Proinflammatory and chemotactic cytokines and their receptors may represent additional therapeutic targets for treatment of schizophrenia.

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.

Cytokines, neurophysiology, neuropsychology, and psychiatric symptoms

Recent research has overcome the old paradigms of the brain as an immunologically privileged organ, and of the exclusive role of neurotransmitters and neuropeptides as signal transducers in the central nervous system. Growing evidence suggests that the signal proteins of the immune system - the cytokines - are also involved in modulation of behavior and induction of psychiatric symptoms. This article gives an overview on the nature of cytokines and the proposed mechanisms of immune-to-brain interaction. The role of cytokines in psychiatric symptoms, syndromes, and disorders like sickness behavior, major depression, and schizophrenia are discussed together with recent immunogenetic findings.

Antipsychotic drugs suppress the AKT/NF-κB pathway and regulate the differentiation of T-cell subsets

Antipsychotic drugs (APDs) are commonly used to ease the symptoms of schizophrenia; however, these same drugs also have an effect on the human immune system. Our previous studies have shown that risperidone and clozapine effectively decrease the production of IFN-γ for CD4(+) T-cells in PBMC. In contrast, haloperidol causes an increase in the production of IFN-γ for CD4(+) T-cells in PBMC. In this study we show that risperidone and clozapine can reduce Th1 cell differentiation and T-bet expression. The differentiation of Th1 cells was reduced in clozapine or risperidone treated PBMC by inhibiting the phosphorylation of AKT but not STAT-4. Typical APD, haloperidol, had the opposite effect in regulating T cell differentiation when compared with atypical APDs including risperidone and clozapine. Haloperidol decreased the expression of GATA-3, a Th2-related transcription factor, by inhibiting NF-κB activation rather than STAT-6 phosphorylation and thus decreased Th2 differentiation. In addition, chronic risperidone and clozapine treatment reduces the IFN-γ producing CD4(+) T-cell population within PBMC. In conclusion, this study suggests that APDs do indeed regulate the body's immune response and therefore all APDs should have their own patent in regulating immune responses.

Effects of haloperidol and risperidone on the expression of heat shock protein 70 in MK-801-treated rat C6 glioma cells

Non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists such as dizocilpine (MK-801) produce schizophrenia-like psychosis in humans and induce the expression of heat shock protein 70 (HSP70) in rats. The present study examines the effects of antipsychotic drugs, haloperidol and risperidone, on the expression of HSP70 produced by MK-801 in rat C6 glioma cells. After pretreating with haloperidol and risperidone for 1 h, 6 h, 24 h and 72 h, respectively, C6 glioma cells were cultivated again in MK-801 for 6 h, and then, the extent of HSP70 expression was measured by immunoblotting using anti-HSP70 monoclonal antibody. The expression of HSP70 induced by MK-801 significantly decreased as the duration of haloperidol pretreatment was extended (p=0.002). Risperidone also increasingly attenuated the expression of HSP70 produced by MK-801 as the duration of pretreatment grew longer (p=0.003). The present findings show that haloperidol and risperidone decrease the HSP70 expression in MK-801-treated rat C6 glioma cells. These results suggest that HSP70 and NMDA receptors may play a significant role in the pathophysiology of schizophrenia.

The ultrastructure of lymphocytes in schizophrenia

OBJECTIVE

Replicated abnormalities in schizophrenia include decreased cellular immunity. The aim of the study was to verify whether there are some abnormalities in the ultrastructure of lymphocytes in drug-free schizophrenic patients.

METHOD

Fifty-nine in-patients with paranoid schizophrenia (DSM-IV 295.30) and 31 normal controls were used. Psychosis severity was assessed by the PANSS psychotic cluster. Electron microscopy and morphometric methods were applied to estimate the frequency and ultrastructural parameters of small, large, large activated lymphocytes (LAL) (containing 10 and more mitochondria) and of atypical lymphocytes (lymphoblasts, LB).

RESULTS

The frequency of small lymphocytes in schizophrenic patients was lower and that of large lymphocytes, LAL and LB was higher than in controls (all p= < 0.01). The volume density (Vv) of mitochondria in LAL in individuals with schizophrenia was lower than in controls (p<0.05), correlated negatively with the frequency of LB, Vv and number of lysosomes in LB (all p<0.01) and with the psychosis severity (p<0.05). In schizophrenic patients a trend towards positive correlations between the frequency of LB and psychosis severity were found (p<0.07).

CONCLUSION

The data suggest that the excess of LB in schizophrenic patients is associated with the dysfunction of energy metabolism in LAL, and these abnormalities are related to schizophrenia.

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.

IL-2 and IL-4 polymorphisms as candidate genes in schizophrenia

An immune process, characterized by a relative predominance of the T helper-2 (Th2) system and possibly induced by a viral infection,may be involved in the pathophysiology of schizophrenia. In this context, functional polymorphisms in the Interleukin-2 (IL-2) and Interleukin-4 (IL-4) genes appear to be principal candidates for genetic schizophrenia research. Further evidence for these candidate genes comes from several linkage analyses, pointing to susceptibility gene loci on chromosomes 4q and 5q, where the genes coding for IL- 2 and IL-4 are located. We carried out a case-control study including 230 schizophrenic patients and 251 healthy persons, investigating the IL-2 -330 T/G single nucleotide polymorphism (SNP) and the IL-4 -590 C/T SNP. A significant association of the IL-2 -330 TT genotype and of the IL-4 -590 CC genotype with schizophrenia could be identified. Our findings may partly account for the relative predominance of the Th2 system in schizophrenia, although they cannot directly explain this immunological imbalance, but may be related to an altered antiviral immune response in patients with schizophrenia.

COX-2 inhibitors as adjunctive therapy in schizophrenia: rationale for use and evidence to date

A better understanding of the human immune system and its complex interactions has resulted in new insights into the pathoaetiological mechanisms of psychiatric disorders. As a result, new treatment options are being explored. Several findings suggest that an imbalanced immune response is involved in the pathophysiology of schizophrenia. COX-2 inhibitors are known to influence the immune system in a way that may redirect this imbalance. Based on these suggestions, the COX-2 inhibitor celecoxib has been tested as a possible adjunctive therapeutic approach in the treatment of schizophrenia. While the first trial using celecoxib as add-on therapy to an atypical antipsychotic showed a significant beneficial effect, recent studies demonstrated that this effect may be limited to patients with recent-onset schizophrenia.

Th1, Th2 and Th3 cytokine alteration in schizophrenia

BACKGROUND

Several studies have shown that there is an imbalance between T helper 1 (Th1) cytokines and T helper 2 (Th2) cytokines in patients with schizophrenia. The T helper 3 (Th3) cytokine, transforming growth factor beta-1 (TGF-beta1), has been shown to suppress the production of Th1 cytokines. Therefore it is hypothesized that it may play a role in schizophrenia by suppressing overactive Th1 system.

METHODS

We recruited 88 schizophrenic patients and 88 matched controls. The basal plasma concentrations of IFN-gamma (Th1), IL-4 (Th2) and TGF-beta1 (Th3) were studied at the time the patients were admitted to the hospital and following 8 weeks of treatment with antipsychotics.

RESULTS

The detection rate of plasma IFN-gamma and basal plasma TGF-beta1 level were significantly higher in schizophrenic patients than in controls whereas detection rate of plasma IL-4 was lower in patients. The ratio of Th1/Th2 cytokines (IFN-gamma/IL-4) was higher in schizophrenic patients. Following the neuroleptic treatment, the IFNgamma and TGF-beta1 levels returned to control values, and IL-4 concentration rose above the control value.

CONCLUSION

Schizophrenic patients showed higher Th1/Th2 ratio which is attenuated by effective neuroleptic treatment. It is possible that TGF-beta1 plays a role in reducing the activity of Th1 cytokine.

Immunologic variables in acute mania of bipolar disorder

Macrophages, lymphocytes and their products, may be involved in the pathophysiology of psychiatric disorders. The cell-mediated immune activation response of manic patients during pre-medication and medication stages remains unclear. The purpose of this case-control study was to investigate the plasma levels of immunologic variables, including interleukin (IL)-1 receptor antagonist (IL-1RA), soluble CD 4 (sCD4) and sCD8, and TH1 (interferon [IFN]-gamma and IL-2) and TH2 (IL-4 and IL-10) cytokines in patients with pre-medicated, medicated bipolar mania. The study subjects, aged 16-44 years, were physically healthy patients with Young Mania Rating Scale (YMRS) scores > or =26, and normal controls, aged 19-40 years, were matched for sex. The immune variables were measured in acute mania and in consequent remission (YMRS scores < or =12) among bipolar patients. The plasma levels of IL-1RA, sCD4, and sCD8 were found significantly increased in pre-medicated acute manic patients as compared to normal controls. But only IL-1RA and sCD8 were found different in remitted bipolar patients as compared to normal controls. For TH1 cytokines, culture supernatant level of IFN-gamma was found significantly lower in manic patients of both acute and remission stages as compared to normal controls. No significant difference was found in IL-2 level in pre-medicated acute manic patients compared to controls. For TH2 cytokines, no significant differences in IL-4 and IL-10 levels were observed. We showed that cell-mediated immune response was activated in patients with bipolar disorder during the pre-medication, medication, and the remission stages. Our study findings suggest that the immune-modulation in patients with bipolar disorder may be abnormal.

Membrane polyunsaturated fatty acids and CSF cytokines in patients with schizophrenia

Findings to date provide evidence that altered membrane structure and function are present in patients with either first-episode or chronic schizophrenia, suggesting defects in phospholipid metabolism and cell signaling in schizophrenia. The purpose of this investigation is to test whether decreased membrane polyunsaturated fatty acids (PUFAs) were associated with an increased secretion of proinflammatory cytokines. Thus, we measured interleukin 6 (IL-6) and interleukin 10 (IL-10) in cerebrospinal fluid (CSF) of patients with chronic schizophrenia as well as PUFAs of red blood cell (RBC) membranes from the same individuals. A significant and inverse correlation was found between CSF IL-6 (not IL-10) and RBC membrane PUFAs levels in both haloperidol-treated and medication-free patients with schizophrenia. Specifically, such an association was found in the n-6 (18:2, 20:4, and 22:4) and, to a lesser extent, the n-3 fatty acids. Taken together, the present findings suggest that decreased membrane PUFAs may be related to an immune disturbance in schizophrenia, possibly resulting from an increased phospholipase A2 activity mediated through the proinflammatory cytokines.

Interleukin-10 gene promoter polymorphism is not associated with schizophrenia in the Korean population

The present study was aimed at examining the interleukin (IL)-10 gene promoter region polymorphic variants in patients with schizophrenia in the Korean population. Two hundred and thirty-three Korean patients diagnosed to have schizophrenia on the basis of Diagnostic and Statistical Manual of Mental Disorders (4th edn; DSM-IV) and 181 normal healthy controls participated in the present study. The DNA was extracted from whole blood using proteinase K and the IL-10 gene promoter region was amplified by polymerase chain reaction. Gene typing was performed by restriction fragment length polymorphism and single-strand conformation polymorphism. Distribution of the alleles and haplotypes in patients with schizophrenia was not significantly different from those of controls. The present study suggests that IL-10 gene promoter polymorphism is not associated with the development of schizophrenia in the Korean population.

Decreased production of interleukin-2 (IL-2), IL-2 secreting cells and CD4+ cells in medication-free patients with schizophrenia

There are a number of indications that schizophrenia is associated with changes in the immune system. Although functional studies have mostly demonstrated decreased in vitro production of IL-2 by peripheral blood mononuclear cells (PBMCs) stimulated with mitogen, the reason is unclear. The aim of the study was to explore the relationship between IL-2 production and CD4+ cells which mainly secret IL-2 in non-Caucasian patients with schizophrenia. Blood CD4+ cells and mitogen-stimulated IL-2 secreting cells identified by an immunohistochemical study with the alkaline phosphatase/anti-alkaline phosphatase (APAAP) technique, and in vitro IL-2 production with radioimmunometric assay (RIA) were measured in 30 schizophrenic patients and 30 normal control subjects matched for sex, age and race. The results showed that blood CD4+ cells and mitogen-induced IL-2 secreting cells and IL-2 production were significantly lower in schizophrenic subjects than in the normal controls. There was significantly positive correlation between CD4+ cells and IL-2 production in normal controls but not in patients. These findings suggest that immune disturbance may be present in schizophrenic patients. The lower in vitro IL-2 production is probably related to the decreased number of T-cells that secret IL-2, as well as to the intrinsic disorder of the patients' T cells.

Polymorphism of CTLA-4 gene at position 49 of exon 1 may be associated with schizophrenia in the Korean population

This study was carried out to investigate the association of a polymorphism of the CTLA-4 gene, at position 49 of exon 1, with schizophrenia in the Korean population. Among Korean patients diagnosed with schizophrenia according to DSM-IV, 116 patients who met the selection criteria were recruited for the study. One hundred and forty-nine normal healthy Koreans from the Catholic Hemopoietic Stem Cell Information Bank, were used as a normal control group. DNA was extracted from whole blood using proteinase K and the CTLA-4 gene region was amplified by polymerase chain reaction. Geneo typing was performed by single strand conformation polymorphism (SSCP). The genotype and allele distribution in patients with schizophrenia was significantly different from that seen in the control group. This study suggests a putative role of the CTLA-4 gene polymorphism at position 49 of exon 1 for schizophrenia in the Korean population, although the detailed mechanisms remained to be elucidated.

Possible mechanisms of panic attack and schizophrenia via APUD system

Psilocybin poisoning produces biphasic reactions composed of a schizophrenic phase and a panic attack-like phase. There is a time lag of several hours between phases, which may be considered an accumulation time in certain sites between the gut and the brain. So far as 5-hydroxytryptamine (5-HT) congeners are concerned, no sites are to be found except the amine precursor uptake and decarboxylation (APUD) system. It is postulated that argyrophil cells (AC) in the foregut, neuroepithelial bodies (NEB) in the lung, and raphe nuclei (RN) in the brainstem axis are relevant to mental disorders. Schizophrenia might be due to the massive destruction of APUD cells, and the paroxysmal release of 5-HT with peptides and panneuroendocrine markers from NEB might be the cause of panic attack.

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.

Identification of antibodies to heat shock proteins 90 kDa and 70 kDa in patients with schizophrenia

OBJECTIVES

Recent reports of antibodies to heat shock proteins 60kDa (HSP60) and HSP70 suggested that antibodies to the heat shock protein that plays a protective role against environmental stresses in a cell might be related to the pathogenesis of schizophrenia, although the antibody to HSP90 had not yet been identified in patients with schizophrenia. In this study, we tried to elucidate the specific involvement of the autoimmunity to HSPs in the pathogenesis and development of schizophrenia.

METHODS

Antibodies to HSP90 and HSP70 in 90 patients with schizophrenia and in 83 normal controls were measured by enzyme-linked immunosorbent assay (ELISA) coupled with the avidin-biotin system. In the patients, the association between antibody levels and clinical variables were sought. In addition, changes in antibody levels after treatment with antipsychotic medication were investigated.

RESULTS

Eighteen (20.0%) of the 90 patients showed 'high' levels of antibody to HSP90 above a cutoff value, and 28 (31.1%) of those showed 'high' antibody levels to HSP70. On the other hand, only four (4.8%) of the normal controls showed 'high' HSP90 antibody levels, and one (1.2%) of these showed 'high' antibody level to HSP70. The distribution of elevated HSP90 antibody was significantly associated with that of elevated HSP70 antibody in the patients with schizophrenia. The patients with 'high' levels of antibody to HSP70 showed higher initial Brief Psychiatric Rating Scale (BPRS) scores and showed greater clinical improvement than those with 'low' levels, while the patients with 'high' levels of antibody to HSP90 did not. The frequency of patients with high levels of antibody to HSP70 was decreased significantly after 6 weeks of antipsychotic treatment, while the frequency of patients with high levels of antibody to HSP90 was not.

CONCLUSIONS

Our results presented the presence of abnormal immune reactivity involving antibody to HSP90 and antibody to HSP70 in a subset of patients with schizophrenia. Differential patterns of distribution, of the association with clinical symptom severity, and of the changes of levels with treatment suggested the possibility that these two antibodies might be involved specifically in the pathogenesis of schizophrenia.

Cytokine serum levels, autologous mixed lymphocyte reaction and surface marker analysis in never medicated and chronically medicated schizophrenic patients

A number of immunological parameters were studied in 82 DSM-III-R diagnosed schizophrenic patients (53 first drug-naive and 29 medicated chronic patients) as well as 62 healthy blood donors. The serum levels of interleukin-2 (IL-2), interleukin-1 beta (IL-1beta) and tumour necrosis factor-alpha (TNF-alpha) were measured and correlated with cellular immunity, as assessed by the autologous mixed lymphocyte reaction (AMLR). T lymphocyte subsets were also examined. The above immune parameters were reassessed in a subgroup of 11 first-episode, drug-naive patients 1month after neuroleptic medication. IL-2 serum levels were significantly lower, and IL-1beta and TNF-alpha were significantly higher in schizophrenic patients compared with healthy donors (P<0.001); no significant difference was observed between the two patient groups (medicated and not medicated). Abnormal cytokine serum levels were associated with decreased AMLR responses in vitro. Increased percentages of activated CD4+ and CD16+ natural killer cells, as well as cells expressing ICAM-1 adhesion molecules and IL-2 specific receptors, were detected in the patients. Immunophenotype studies revealed a higher percentage of cells expressing IL-2 receptors in medicated chronic schizophrenic patients compared with drug-naive patients. The abnormal cytokine production in vivo, along with the low AMLR responses in vitro, and the high percentage of activated CD4+ lymphocytes presented in this study suggest alterations in the immune system of schizophrenic patients (medicated or not medicated) consistent with immune activation.

Immunological dysfunction in schizophrenia: a systematic approach

BACKGROUND

In the present study, immunological alterations were investigated as one possible factor contributing towards the pathogenesis of schizophrenia. Specifically cellular changes, deviating cytokine production and interfering variables were studied in order to improve our understanding of how these factors interact.

METHOD

44 acutely ill schizophrenics were compared with matched healthy controls. Cell numbers were determined by flow cytometry and cytokine production by whole blood assay and ELISA. A criss-cross technique was employed for the assessment of interfering serum factors.

RESULTS

Cell counts for leukocytes, lymphocytes, pan T cells, activated T cells and the absolute B cell count of the schizophrenic patients were all within normal limits. The absolute and relative monocyte counts, the number of IL-2 receptor carrying T cells and the relative B cell count were slightly elevated. IL-2 and IFN-gamma production were increased while IL-10 production, the sIL-2R and cortisol levels remained unchanged. No interfering serum factors were detected.

CONCLUSION

The deficient production of TH-1 cytokines in schizophrenia is not due either to a changed number of immunocompetent cells or to a counterregulation of the TH-2 cytokine IL-10. Serum factors in in vitro testing are not responsible for the deficient cytokine production.

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.

Plasma levels of cytokines and soluble cytokine receptors in psychiatric patients upon hospital admission: effects of confounding factors and diagnosis

It has been hypothesized that the immune system plays a pathogenetic role in psychiatric disorders, in particular in major depression and schizophrenia. This hypothesis is supported by a number of reports on altered circulating levels and in vitro production of cytokines in these disorders. However, the respective evidence is not consistent. This may be in part due to an incomplete control for numerous confounding influences in earlier studies. We investigated the plasma levels of cytokines and soluble cytokine receptors in psychiatric patients (N = 361) upon hospital admission and compared the results to those obtained in healthy controls (N = 64). By multiple regression analysis we found that circulating levels of interleukin-1 receptor antagonist (IL-1Ra), soluble IL-2 receptor (sIL-2R), tumor necrosis factor-alpha (TNF-alpha), soluble TNF receptors (sTNF-R p55, sTNF-R p75) and IL-6 were significantly affected by age, the body mass index (BMI), gender, smoking habits, ongoing or recent infectious diseases, or prior medication. Cytokine or cytokine receptor levels were significantly increased in patients treated with clozapine (sIL-2R, sTNF-R p75), lithium (TNF-alpha, sTNF-R p75, IL-6) or benzodiazepines (TNF-alpha, sTNF-R p75). Taking all these confounding factors into account, we found no evidence for disease-related alterations in the levels of IL-1Ra, sIL-2R, sTNF-R p75 and IL-6, whereas levels of TNF-alpha and sTNF-R p55 in major depression and sTNF-R p55 in schizophrenia were slightly decreased compared to healthy controls. We conclude that, if confounding factors are carefully taken into account, plasma levels of the above mentioned cytokines and cytokine receptors yield little, if any, evidence for immunopathology in schizophrenia or major depression.

T-cell subsets in schizophrenia: a comparison between drug-naive first episode patients and chronic schizophrenic patients

T-cell subsets (CD3+, CD4+, CD8+, NK-cells) and the CD4+/CD8+ ratio were measured in 56 schizophrenic patients admitted to hospital with an acute psychosis. Thirty-five patients with chronic schizophrenia and 21 drug-naive first episode schizophrenic patients were compared with 16 healthy controls. T-cell subsets were quantified in the acute state of the illness (day 0), after 7 days of treatment and at the time of discharge. In the acute state, schizophrenic patients showed higher CD3+ and CD4+ cells (p = 0.05) and a higher CD4/CD8 ratio (p = 0.02) than healthy controls, while NK-cells were lower (p = 0.05). In first episode patients, all T-cell alterations normalized during treatment. In the chronic group the ratio remained high, whereas the initially low number of NK-cells normalized over time. These findings, supporting immune system dysregulation in schizophrenia, are discussed in relation to psychopathology, the stage of illness and effects of medication.

Leukocyte differentials predict short-term clinical outcome following antipsychotic treatment in schizophrenia

BACKGROUND

The majority of patients with schizophrenia and many of their unaffected siblings exhibit a relative granulocytosis and lymphopenia. To characterize these abnormalities better, we examined leukocyte differentials and organ nonspecific autoantibodies in relationship to intake phenomenology and short-term clinical outcome.

METHODS

We studied patients with schizophrenia (n = 81) and their siblings (n = 18). At intake assessment, about one-half of the probands (n = 38) were neurolepticnaive first-episode patients; the remainder were medication-free for at least 2 weeks. Hematologic indices were obtained at intake assessment, and psychiatric symptomatology was assessed at baseline and following 6 months of clinically determined treatment.

RESULTS

A relative granulocytosis and lymphopenia prospectively predicted poorer recovery in positive, but not negative, symptoms after 6 months of antipsychotic treatment. Abnormal leukocyte proportions were specific to patients who presented with clinically significant positive symptomatology at intake. In contrast, clinically significant negative symptoms were only evident in a small subgroup of patients who were positive for antinuclear autoantibodies and/or rheumatoid factor.

CONCLUSIONS

Future research should further test the hypothesis that a relative granulocytosis and lymphopenia reflect genetic loading for the pathophysiologic determinants of positive symptoms. Future research also should determine the etiologic significance of organ nonspecific autoimmunity in predominantly negative symptom schizophrenia.

Increased soluble interleukin 2 receptor levels in schizophrenia

Immunological mechanisms have been implicated in schizophrenia, but laboratory results have been variable. We evaluated soluble interleukin 2 receptor (sIL2R alpha) levels in sera of Irish patients with schizophrenia. Twenty-seven patients, 12 females and 15 males, with schizophrenia or schizophreniform psychosis, were sampled, along with 32 controls. Diagnosis was made using the Structured Clinical Interview for DSM IIIR. All but one of the patient group were in the first fortnight of an acute hospital admission. Soluble IL2R alpha levels were measured by ELISA. Soluble IL2R alpha levels were significantly higher (two-tailed p = 0.0019) in patients (median = 1010.4 pg/ml, range = 748.7-5673.3 pg/ml) than in controls (median = 792.3 pg/ml, range = 399.6-1479.5 pg/ml). The elevated sIL2R alpha levels in an Irish population with schizophrenia are consistent with other reports and support the implication of immunological mechanisms in this disorder.

Immunophenotypic studies on atypical lymphocytes in psychiatric patients

By using phase-contrast microscopy combined with a fluorescent staining technique, the frequency of blast-type atypical lymphocytes (BTALs) appearing in peripheral blood and the phenotypic expression of their surface antigens were studied in 24 patients with schizophrenia, 16 with mood disorder and 14 healthy controls. BTALs were classified as being stimulated or activated cells, morphologically characterized by their large size, dark cytoplasm, a hollow perinuclear containing a few granules and finely dispersed chromatin structures with a few evident nucleoli. A significantly higher number of BTALs were found in the schizophrenic patients compared with healthy control subjects or patients with mood disorder. Further, there was a significant difference in the frequency of BTALs between patients with mood disorder and healthy control subjects. No significant difference in the frequency of BTALs was found between the schizophrenic patients with and without medication. Immunostaining of BTALs revealed that these cells consisted of B, T and non-B, non-T cell subpopulations. Contrary to our expectations, the T cell was only one third of the BTAL population. HLA-DR and CD38 were expressed on most BTALs (> 70%), while CD25, an early activation marker of T cells was rarely found on BTALs (< 0.3%). The differences in activated lymphocyte populations which appeared as morphologically atypical in the circulation among some psychiatric patients and infectious or autoimmune diseases are discussed. This is the first report on populations of BTALs.

Short and long-term immunosuppressive effects of clozapine and haloperidol

In line with the autoimmune hypothesis of schizophrenia we have tested in this study whether the commonly used neuroleptics, clozapine and haloperidol can also act as systemic immunosuppressants. Twenty one hospitalized chronic schizophrenic patients participated in the study. Five were free of neuroleptic treatment while the other 16 were under chronic treatment with either clozapine (n = 8), or haloperidol (n = 8). Fourteen age matched normal subjects served as the control group. Conventional in vitro mitogenic stimulation of peripheral blood lymphocytes with phytohaemagglutinin (PHA) indicated a clear suppression of responsiveness of approximately 50% in all treated patients. The PHA response of the untreated patients was virtually identical to that of the control group. The in vitro effect of haloperidol and clozapine on PHA stimulation of lymphocytes from normal subjects was determined by 3H-thymidine uptake and secretion of interleukin-2, interleukin-4 and interferon-gamma. Both clozapine and haloperidol suppressed thymidine incorporation and cytokine secretion at a drug concentration of above 1 microM, reaching full suppression at 50 microM. Similar suppressive effects of clozapine and haloperidol were also observed in mixed lymphocyte reaction of mouse lymphocytes. Assays with radioactive ligands indicated that clozapine is not incorporated into the lymphocytes but presumably exerts its action by binding to specific surface sites. The long term immune suppression induced by neuroleptic treatment may inhibit putative autoimmune responses against neurological sites and could thus act synergistically with the direct antagonistic action on brain receptors for the overt amelioration of psychotic behaviour.

An association between increased serum-soluble interleukin-2 receptors and a disturbance in muscle force in schizophrenic patients

1. Serum-soluble interleukin-2 receptors (SIL-2Rs), a sign of immune activation, are increased in approximately 30% of schizophrenic subjects. 2. In a recent publication the authors found that SIL-2Rs were particularly elevated in schizophrenic subjects with tardive dyskinesia (TD). 3. This paper investigates the relationship between muscle force instability and SIL-2Rs in 32 schizophrenic patients, 10 of whom were neuroleptic-naive. 4. The authors hypothesized that there would be a positive correlation between increased levels of SIL-2Rs and muscle force instability. 5. Serum SIL-2Rs and muscle force instability were positively correlated (r = 0.54, p < .001) in the schizophrenic patients, and this correlation held even for the subset of neuroleptic-naive patients (r = .73, df 8, p = .016). 6. These findings suggest that there is an important correlation between immune activation and muscle force instability in schizophrenic patients.

Plasma levels of interleukin-6 and tumor necrosis factor alpha in chronic schizophrenia: effects of clozapine treatment

Plasma levels of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF alpha) were assessed in 17 chronic schizophrenic patients who had been drug-free for 3 weeks and in 17 age- and sex-matched healthy subjects. Plasma concentrations of both cytokines were measured again in 12 patients after a 10-week treatment with clozapine. Compared with healthy controls, drug-free schizophrenic patients exhibited similar plasma IL-6 concentrations, but significantly higher levels of TNF alpha. After clozapine treatment, blood concentrations of TNF alpha fell to normal levels. These preliminary data support an immune activation in drug-free schizophrenic patients and an effect of clozapine on immune parameters.

Neurobehavioral alterations in autoimmune mice

Inbred MRL, NZB and BXSB strains of mice spontaneously develop a systemic, lupus-like autoimmune disease. The progress of autoimmunity is accompanied with a cascade of behavioral changes, most consistently observed in tasks reflective of emotional reactivity and the two-way avoidance learning task. Given the possibility that behavioral alterations may reflect a detrimental consequence of autoimmune-inflammatory processes and/or an adaptive response to chronic malaise, they are tentatively labeled as autoimmunity-associated behavioral syndrome (AABS). It is hypothesized that neuroactive immune factors (pro-inflammatory cytokines, brain-reactive antibodies) together with endocrine mediators (corticotropin-releasing factor, glucocorticoids) participate in the etiology of AABS. Since AABS develops natively, and has a considerable face and predictive validity, and since the principal pathway to autoimmunity is known, AABS may be a useful model for the study of CNS involvement in human autoimmune diseases and by extension, for testing autoimmune hypotheses of several mental disorders (major depression, schizophrenia, Alzheimer's disease, autism and AIDS-related dementia).

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

Dysfunction of T-cell mediated immunity, which is indicated by deficient production of interleukin-2 (IL-2) and elevated levels of the soluble interleukin-2 receptor (sIL-2R), has been consistently demonstrated in schizophrenia. Recent studies on interferon-gamma (IFN-gamma), a cytokine which is also produced by T-helper cells, have indicated a lowered production in acute schizophrenia. It is not known whether this deficit is restricted to cases of acute schizophrenia or whether it is also present in residual schizophrenia and in first degree relatives, and therefore might be associated with genetic liability to the disease. We investigated 27 individuals (schizophrenics and first degree relatives) of 6 families with multiple occurrence of schizophrenia and 27 age- and sex-matched healthy controls. The production of IFN-gamma was lowered only in the acutely ill schizophrenic individuals, when compared to both controls and first degree relatives. In the context of current knowledge, this result indicates that the production of IFN-gamma can be discussed as a marker of acute exacerbation of schizophrenia, but it is not likely to represent a phenotypic marker of a genetic trait associated with the disease.

Increased production of interleukin-2 (IL-2) but not soluble interleukin-2 receptors (sIL-2R) in unmedicated patients with schizophrenia and schizophreniform disorder

This study investigated immune activation, as measured by production of interleukin-2 (IL-2) and soluble interleukin-2 receptors (sIL-2R) from stimulated lymphocytes, in schizophrenia and schizophreniform disorder. The study included 13 neuroleptic-free patients, 13 medicated patients and 13 age- and sex-matched control subjects. Production of IL-2 and sIL-2R by peripheral blood mononuclear cells (PBMCs) was measured after in vitro stimulation with phytohaemagglutinin (PHA). Patients' symptoms were rated on the Scales for Assessment of Positive (SAPS) and Negative Symptoms (SANS) and the Brief Psychiatric Rating Scale (BPRS). IL-2 production by stimulated lymphocytes was significantly elevated in neuroleptic-free patients compared with both medicated patients and control subjects. IL-2 production was inversely correlated with the SAPS subscales of bizarre behaviour and formal thought disorder. The pattern of increased IL-2 production is in contrast to previous findings in patients with schizophrenia. Significant associations with clinical rating scores suggest that IL-2 production may vary in different biological subgroups of schizophrenia and schizophreniform disorder.

Leukocytes and organ-nonspecific autoantibodies in schizophrenics and their siblings: markers of vulnerability or disease?

To determine whether leukocyte counts and organ-nonspecific autoantibodies mark familial vulnerability for schizophrenia and/or the disease itself, we examined 92 patients with schizophrenia and 94 unrelated, demographically balanced, healthy individuals. In addition, for 19 of the probands, one of their nonschizophrenia, full siblings also was recruited. At the time of the blood draw, most probands (87%) had been free of medications for a minimum of 2 weeks and about half were neuroleptic-naive, first-episode patients. Results indicate that a relative lymphopenia in the context of a relative granulocytosis appears to mark familial vulnerability for schizophrenia, whereas an absolute monocytosis appears to mark spectrum manifestations of the clinical phenotype. The former observation is consistent with the hypothesis that the etiology of schizophrenia is immunologically mediated, whereas the latter is consistent with emerging evidence that an inflammatory process is associated with the expression of the disorder. Neither antinuclear antibody nor rheumatoid factor emerged as liability or disease markers.

Lower plasma CC16, a natural anti-inflammatory protein, and increased plasma interleukin-1 receptor antagonist in schizophrenia: effects of antipsychotic drugs

Recently, it was suggested that in vivo activation of the monocytic and T-lymphocytic arms of cell-mediated immunity (CMI) may occur in schizophrenia and that antipsychotic drugs may modify CMI. The aim of the present study was to examine plasma soluble interleukin-2 receptor (sIL-2R), soluble suppressor/cytotoxic antigen (sCD8), interleukin-1 receptor antagonist (IL-1RA), and Clara cell protein (CC16) concentrations in normal controls, nonmedicated schizophrenic patients, and schizophrenic patients treated with risperidone or loxapine. Plasma concentrations of IL-1RA were significantly higher in nonmedicated schizophrenic patients than in normal controls. Plasma CC16 was significantly lower in nonmedicated and loxapine-treated schizophrenic patients than in normal controls, whereas risperidone-treated patients had plasma CC16 levels which were not significantly different from normal controls. Plasma CC16 levels were significantly and positively related to age at onset of schizophrenia. Plasma sIL-2R was significantly higher in schizophrenic patients who were treated with risperidone than in normal controls and nonmedicated schizophrenic patients. The results show that (i) schizophrenia is accompanied by an activation of the monocytic arm of CMI (i.e., increased plasma IL-1RA) and lower plasma levels of a natural anti-inflammatory and immunosuppressive agent, i.e. CC16, and that the latter may constitute a trait market of schizophrenia; and that (ii) chronic treatment with atypical antipsychotic agents, i.e., risperidone, may normalize lower plasma CC16 and increase plasma sIL-2R.

Investigations of cytokine production in whole blood cultures of paranoid and residual schizophrenic patients

In an attempt to define potential immunological dysfunctions in schizophrenia, we determined the production of interleukin-2 (IL-2), interleukin-4 (IL-4), interferon-gamma (IFN-gamma), and soluble IL-2 receptor (sIL-2R) in a whole-blood assay after stimulation with phytohemagglutinin (PHA) as well as the serum concentrations of sIL-2R. Because CD4+CD45RO+T cells are the main producers of IFN-gamma, we determined the percentage of these cells, as well as of panT, CD4+T, and CD8+T cells, by flow cytometry. A whole-blood count was performed in addition. Two groups of patients were examined, paranoid-type and residual-type schizophrenics. The numbers of both monocytes and neutrophils, but not of lymphocytes, were increased significantly in the schizophrenic sample. The IFN-gamma production of the schizophrenics as a whole group, and of the paranoid patients, was reduced significantly in comparison with the control group (p < or = 0.05). The residual patients produced less IFN-gamma than the controls, but more than the paranoid patients. The latter differences did not reach statistical significance. The production of IL-4, which physiologically antagonizes the production of IFN-gamma, was not significantly higher in the patient group. No changes in the lymphocyte subpopulations were observed. The production of IL-2 showed a trend toward reduction in paranoid patients, but not in residual schizophrenics. The serum sIL-2R levels were elevated slightly in schizophrenics when compared with controls. In order to rule out a possible effect of cortisol on cytokine production, 20 schizophrenics were compared with 20 age- and gender-matched controls. However, neither elevated cortisol levels were detected in the schizophrenic sample, nor significant intercorrelations between cortisol levels and cytokine production, or levels of sIL-2R, respectively. In summary, our data reinforce the possibility of immune dysfunction in schizophrenia and point to the possible relevance of disease subgroups in this respect.

Immunological influences in attention-deficit disorder and schizophrenia; is there a link between these two conditions?

This paper aims to explore the influence of the immune system on the pathobiochemistry of movement disorders (Tourette syndrome, obsessive compulsive disorders and attention-deficit disorder, with and without hyperactivity) and schizophrenia. In children, a temporal relationship has been observed between contraction of a group A beta-hemolytic streptococcal infection and subsequent presentation with one of the movement disorders. Pathology investigations reveal that elevated antineuronal antibodies are associated with movement disorders. Similarly, elevations in interleukin-1 beta and interleukin-6 have been reported in schizophrenia. It is now known that the immune system can be activated by conditions other than a viral or bacterial infection, such as: neurological insult, neurotoxicity--endogenous and environmental, neurotransmitter and cholesterol dysregulation. These latter avenues of immune system activation will be explored with respect to schizophrenia.

Interleukin-2 as a neuroregulatory cytokine

Interleukin-2 (IL-2), the cytokine also known as T-cell growth factor, has multiple immunoregulatory functions and biological properties not only related to T-cells. In the past decade, substantial evidence accumulated to suggest that IL-2 is also a modulator of neural and neuroendocrine functions. First, extremely potent effects of IL-2 on neural cells were discovered, including activities related to cell growth and survival, transmitter and hormone release and the modulation of bioelectric activities. IL-2 may be involved in the regulation of sleep and arousal, memory function, locomotion and the modulation of the neuroendocrine axis. Second, the concept that IL-2 could act as a neuroregulatory cytokine has been supported by reports on the presence in rodent and human brain tissues of IL-2-like bioactivity, IL-2-like immunoreactivity, IL-2-like mRNA, IL-2 binding sites, IL-2 receptor (IL-2R alpha) and beta chain mRNA and IL-2R immunoreactivity. IL-2 and/or IL-2R molecules mainly localize to the frontal cortex, septum, striatum, hippocampal formation, hypothalamus, locus coeruleus, cerebellum, the pituitary and fiber tracts, such as the corpus callosum, where they are likely expressed by both neuronal and glial cells. Although the molecular biology of the brain IL-2/IL-2R system (including its relation to IL-15/IL-15R alpha) is not yet fully established by cloning and complete sequencing of all respective components, similarities (and to some extent differences) to peripheral counterparts are now apparent. The ability of IL-2 to readily penetrate the blood-brain barrier further suggests that this cytokine could regulate interactions between peripheral tissues and the central nervous system. Taken together, these data suggest that IL-2 of either immune and CNS origin can have access to functional IL-2R molecules on neurons and glia under normal conditions. Additionally, dysregulation of the IL-2/IL-2 receptor system could lead or contribute to functional and pathological alterations in the brain as in the immune system. Understanding the neurobiology of the IL-2/IL-2 receptor system should also help to explain neurologic, neuropsychiatric and neuroendocrine side effects occurring during IL-2 treatment of peripheral and brain tumors. Immunopharmacological manipulation either aiming at the activation or suppression of IL-2 signaling should consider functional interference with constitutive and inducible IL-2 receptors on brain cells in order to fulfil the high expectations associated with the use of this cytokine as a promising agent in immunotherapies, especially of brain tumors.

Interleukin-2 and interleukin-6 in schizophrenia and mania: effects of neuroleptics and mood stabilizers

There is some evidence that schizophrenia may be accompanied by alterations in cell-mediated immunity (CMI) and that antipsychotic agents may modulate CMI. The purpose of this study was to investigate the plasma levels of interleukin-6 (IL-6), soluble IL-6 receptor (sIL-6R), sIL-2R, and transferrin-receptor (TfR) in schizophrenia and mania, and the effects of treatment with neuroleptics or mood stabilizers on these variables. The subjects were 14 schizophrenic patients, 10 manic patients and 21 healthy volunteers. The above immune variables were measured in baseline conditions and after treatment with neuroleptics in schizophrenic patients and valproate in manic patients. Plasma concentrations of IL-6, sIL-6R, sIL-2R and TfR were significantly higher in the combined group of psychotic patients than in healthy volunteers. Plasma IL-6 was significantly higher in schizophrenic patients, while plasma sIL-6R and sIL-2R were significantly higher in mania than in normal controls. In schizophrenic patients, plasma levels of IL-6, sIL-6R and TfR were significantly lower after treatment with neuroleptics than before treatment. No significant effects of valproate on the immune-inflammatory markers could be found in the manic patients. It is suggested that activation of CMI may occur in both schizophrenia and mania and that neuroleptics may have immunosuppressive effects through suppression of IL-6 or IL-6R-related mechanisms.

Plasma-soluble interleukin-2 and transferrin receptor in schizophrenia and major depression

This study was carried out to examine some components of in vivo immune function in major depression and schizophrenia. Toward this end, plasma concentrations of interleukin-1 beta (IL-1 beta) and IL-6, soluble IL-2 receptor (sIL-2R), and transferrin receptor (TfR) were measured in 28 normal controls, 11 schizophrenics and 13 major-depressed patients. Schizophrenic and major-depressed patients showed significantly higher plasma sIL-2R and TfR than normal controls. There was a trend toward higher plasma IL-6 in the psychiatric patients, and particularly in schizophrenic patients, than in normal volunteers. In normal controls and in the total study group, there were highly significant and positive correlations between plasma TfR and sIL-2R concentrations. It is suggested that schizophrenia and major depression are characterized by immune disorders that may indicate activation of cell-mediated immunity such as T-cell activation.

Viruses, schizophrenia, and bipolar disorder

The hypothesis that viruses or other infectious agents may cause schizophrenia or bipolar disorder dates to the 19th century but has recently been revived. It could explain many clinical, genetic, and epidemiologic aspects of these diseases, including the winter-spring birth seasonality, regional differences, urban birth, household crowding, having an older sibling, and prenatal exposure to influenza as risk factors. It could also explain observed immunological changes such as abnormalities of lymphocytes, proteins, autoantibodies, and cytokines. However, direct studies of viral infections in individuals with these psychiatric diseases have been predominantly negative. Most studies have examined antibodies in blood or cerebrospinal fluid, and relatively few studies have been done on viral antigens, genomes, cytopathic effect on cell culture, and animal transmission experiments. Viral research on schizophrenia and bipolar disorder is thus comparable to viral research on multiple sclerosis and Parkinson's disease: an attractive hypothesis with scattered interesting findings but no clear proof. The application of molecular biological techniques may allow the identification of novel infectious agents and the associations of these novel agents with serious mental diseases.