Production of interferons and lymphokines in leukocyte cultures of patients with schizophrenia

Soluble IL-6 receptors in the serum and cerebrospinal fluid of paranoid schizophrenic patients

Soluble Interleukin-6 receptor (sIL-6R) levels are strongly related to the levels of Interleukin-6 (IL-6), and sIL-6Rs increase the immune activating properties of IL-6. We estimated sIL-6R serum levels in 25 schizophrenic patients and 25 healthy controls. In the patients, SIL-6R-CSF levels were also measured. The psychopathology was rated according to the AMDP system. We found a significant correlation between serum and cerebrospinal fluid (CSF) levels of sIL-6R, suggesting that serum levels may be a meaningful marker for the central action of sIL-6R. Moreover, significant correlations between the paranoid-hallucinatory syndrome and sIL-6R levels both in serum and CSF were observed. This finding suggests that IL-6 plays a role in the paranoid-hallucinatory symptomatology in schizophrenia. This can be understood regarding the influence of IL-6 to the catecholaminergic neurotransmission. The downregulating effects of neuroleptic treatment to sIL-6R demonstrate that the sIL-6R levels are decreased in the whole group of schizophrenic patients compared to controls.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Methodological Issues in Cytokine Measurement in Schizophrenia

There is mounting evidence that inflammation is a major factor in the pathophysiology of schizophrenia. Inflammatory status is commonly ascertained by measuring peripheral cytokine concentrations. An issue concerning research on inflammation and schizophrenia relates to assay methodology. Enzyme-linked immunosorbent assay (ELISA) is the most widely used and the gold standard method used to measure cytokine concentrations. ELISA has a number of limitations. Both ELISA and multiplex are limited by not being able to distinguish between bioactive and inactive molecules and the matrix and heterophilic (auto-) antibody interference. Multiplex assays when combined with gene expression analysis and flow cytometry techniques such as fluorescence-activated cell sorting may be useful to detect abnormalities in specific immune pathways. Peripheral blood mononuclear cells cultures, to evaluate in vitro lipopolysaccharide-induced cytokine production, may be a better technology than measuring cytokines in the serum. The purpose of this paper is to shed light on major methodological issues that need to be addressed in order to advance the study of cytokines in schizophrenia. We make a few recommendations on how to address these issues.

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

BACKGROUND

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Increased Interleukin-17 and decreased BAFF serum levels in drug-free acute schizophrenia

Hypotheses regarding an immune-cytokine basis of schizophrenia have been postulated with controversial findings and a lack of data related to many cytokines. The aim of this study was to assess serum levels of Interferon-γ (IFN-γ), Interleukin-4 (IL-4), Transforming Growth Factor-β (TGF-β), Interleukin-17 (IL-17) and B-cell Activating Factor (BAFF) in schizophrenic patients and to determine correlations between cytokine levels and clinical parameters. Serum cytokine levels were measured with ELISA techniques in 60 neuroleptic-free patients on acute phase of the disease (BPRS≥40) and 28 healthy controls matched for age and sex. Current symptoms were assessed with Brief Psychiatric Rating Scale (BPRS), Positive and Negative Syndrome Scale (PANSS), Scale for the Assessment of Positive Symptoms (SAPS) and Scale for the Assessment of Negative Symptoms (SANS). No significant difference was found between patients and controls regarding IFN-γ serum levels. IL-4 was not detected in both groups. Patients exhibited significantly higher IL-17 and lower BAFF serum levels. IL-17 and BAFF levels were negatively correlated in schizophrenic patients. SANS global score was negatively correlated with IL-17 and positively correlated with IFN-γ serum levels. These results argue against the involvement of Th1 or Th2 population cells in schizophrenia. IL-17 and BAFF could be valuable markers for schizophrenia.

Peripheral interleukin-2 level is associated with negative symptoms and cognitive performance in schizophrenia

Although several studies have pointed to a possible role of interleukin 2 (IL-2) in schizophrenia (SZ), association between IL-2 and the different groups of symptoms has not been explored. The objective of this study was to investigate a possible correlation of peripheral IL-2 levels with symptoms and cognitive performance in patients with SZ. In addition, we compared the plasma levels of IL-2 between patients with SZ and healthy controls. Twenty-nine chronically medicated outpatients with SZ according to DSM-IV were compared with twenty-six healthy controls. The patients were evaluated with the Positive and Negative Syndrome Scale (PANSS), the Calgary Depression Scale for Schizophrenia (CDSS), the Clinical Global Impression (CGI) and the Global Assessment of Functioning (GAF). All the participants had blood collected into EDTA tubes by venipuncture between 9:00 and 10:00AM. Plasma concentrations of IL-2 were determined by cytometric bead array. A computerized neuropsychological battery assessed verbal learning, verbal fluency, working memory, set shifting, executive function, inhibition and intelligence. Patients with SZ had lower levels of IL-2 than healthy controls (p<0.001). In the SZ group, IL-2 levels were positively correlated with scores in the digit span test (rho=0.416, P=0.025) and intelligence (rho=0.464, P=0.011). We also found a negative correlation between IL-2 and total score in the negative subscale of PANSS (rho=-0.447, p=0.015). Our findings suggest that IL-2 may be involved in the mechanisms related to cognitive deterioration and negative symptomatology in schizophrenia.

Autoimmunity, inflammation, and psychosis: a search for peripheral markers

Accumulating evidence supports the view that deregulation of the immune system represents an important vulnerability factor for psychosis. In a subgroup of psychotic patients, the high comorbidity with autoimmune and chronic inflammatory conditions suggests a common underlying immune abnormality leading to both conditions. The reviewed data of affective and nonaffective psychosis show that if immune biomarkers exist for such immune abnormality, they may be found in raised macrophage/monocyte inflammatory activation patterns (monocytosis, high-inflammatory gene expression, raised glucocorticoid receptor β/glucocorticoid receptor α ratio, and high levels of proinflammatory and anti-inflammatory monocyte/macrophage derived cytokines in serum/plasma), reduced T cell numbers/proliferation, and TH1 skewing. This activation of the inflammatory response system may be suggestive for microglia activation, as these cells are the macrophages of the brain. Indeed, there is some evidence of activation of the microglia as detected in positron emission tomography scans and in histopathology, and it is assumed that this activation disturbs the development and function of neuronal circuits in the brain. Further, animal models of psychotic conditions (maternal stress and inflammation paradigms) suggest that such monocyte/microglia activation could be seen as the result of a combination of genetic predisposition and an immune-mediated two-hit model. Infection but also environmental stressors during gestation/early life activate microglia, perturbing neuronal development, thereby setting the stage for vulnerability for later psychotic disorders. A second hit, such as endocrine changes, stress, or infection, could further activate microglia, leading to functional abnormalities of the neuronal circuitry in the brain and psychosis.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

IL-28B genetic variant is associated with the risk of schizophrenia in the Chinese Han population

Schizophrenia is a severe psychiatric disorder. Although its exact cause is unknown, it is widely accepted that environmental factors and genes integrate in the pathogenesis of schizophrenia. 19q13, which contains IL-28B, is a newly identified potential susceptibility locus. IL-28B is a cytokine that functionally has anti-viral activity, but, structurally, is related to the interleukin-10 family. Both virus infection and cytokine changes have been documented in schizophrenia. We selected the single-nucleotide polymorphism rs8099917, which is associated with IL-28B gene expression, to study its relationship to the susceptibility to schizophrenia. A total of 256 Chinese patients with schizophrenia and 329 healthy controls were studied. Both genotype and allele frequencies showed significant differences between patients and normal subjects (p=0.03 and p=0.04, respectively). Our study suggested that the frequency of allele T was a risk factor for the susceptibility of schizophrenia (odds ratio [OR]=1.76, 95% confidence interval [CI]=1.03-3.03). When all subjects were grouped by symptoms, both the genotype and the allele frequency were associated with patients having disorganized speech (genotype: χ(2)=5.75, p=0.02; allele: χ(2)=5.41, p=0.02, OR=3.67, 95% CI=1.14-11.82) and negative symptoms (genotype: χ(2)=5.09, p=0.02; allele: χ(2)=4.80, p=0.03, OR=1.95, 95% CI=1.06-3.56) as well as cognitive symptoms (genotype: χ(2)=5.97, p=0.02; allele: χ(2)=5.53, p=0.02, OR=2.04, 95% CI=1.11-3.74). The results in this study may lead to a better understanding of the etiology of schizophrenia.

Serial mitogen-stimulated cytokine production from continuously ill patients with schizophrenia

Aberrant activation of the immune system has been implicated in an increasingly large number of disease states and can influence cognition, mood, and memory. There is a long and controversial history of reports of immune activation associated with schizophrenia. In this study, we measured mitogen-stimulated cytokine levels serially in 100 medication-stabilized continuously ill subjects with schizophrenia and compared and contrasted them with mitogen-stimulated cytokine levels from 51 normal volunteers. The subjects with schizophrenia had consistently higher mitogen-stimulated IL-2 levels and lower IL-6 levels than the normal volunteers. These effects could not be explained by medications, smoking, or other clinical variables. We conclude that continuously symptomatic medication-stabilized subjects with schizophrenia have a mitogen-stimulated cytokine expression pattern that is suggestive of ongoing immune activation.

Calcitriol inhibits TNF-alpha-induced inflammatory cytokines in human trophoblasts

Elevated placental proinflammatory cytokine release is associated with miscarriage, preterm labor and preeclampsia. Specifically, tumor necrosis factor-alpha (TNF-alpha)-induced cytokines may threaten pregnancy outcome. Since trophoblasts produce calcitriol, a hormone with strong immunosuppressive properties, we assessed the effects of this secosteroid on inflammatory cytokines induced in trophoblasts by challenge with TNF-alpha. The effects of calcitriol on synthesis of mRNAs encoding interleukin-6 (IL-6), interferon-gamma (IFN-gamma), and TNF-alpha were measured by real time RT-PCR. Secreted cytokines were quantified by ELISA. The effects of TNF-alpha on CYP24A1, chorionic gonadotropin (hCG), 3beta-hydroxysteroid dehydrogenase (HSD3B1) and P(450)-aromatase (CYP19) mRNA expression were also studied. TNF-alpha stimulated IL-6, IFN-gamma and its own expression more than 3-fold over controls (P<0.05). Calcitriol inhibited the expression profile of inflammatory cytokine genes in a dose-response manner (P<0.05). This effect was prevented by addition of the vitamin D receptor antagonist TEI-9647. TNF-alpha also significantly inhibited expression of hCG, HSD3B1 and CYP19 genes, and stimulated CYP24A1 gene expression. These data show that calcitriol prevents TNF-alpha induction of inflammatory cytokines through a process likely to be mediated by the vitamin D receptor. We conclude that TNF-alpha inhibits placental hormone synthesis and stimulates calcitriol catabolism by regulating enzymes involved in these processes.

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.

Monocytic, Th1 and th2 cytokine alterations in the pathophysiology of schizophrenia

A growing body of evidence suggests that changes in the serum levels and cellular production of various cytokines are associated with the immunological abnormalities of schizophrenia. Several studies have examined alterations in T helper type 1 (Th1) and T helper type 2 (Th2) cytokines in schizophrenia. We explored monocytic, Th1 and Th2 cytokines in 43 schizophrenia patients and 50 normal controls. The mitogen-induced production of tumor necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), IL-4, gamma-interferon (IFN-gamma) and IL-2 was measured with enzyme-linked immunosorbent assays before and after antipsychotic treatment. IL-6 and TNF-alpha production by schizophrenic patients was significantly higher than by normal controls, while IL-2, IL-4 and IFN-gamma production was significantly lower in schizophrenic patients. After 6 weeks of antipsychotic treatment, IL-6 and TNF-alpha production was significantly decreased, while IL-4, IFN-gamma and IL-2 productions were not significantly changed. Our results suggest that increased monocytic cytokines and decreased Th1 and Th2 cytokines may be associated with the immunopathogenesis of acute psychotic schizophrenia, and that antipsychotics may play an important role in immune response by decreasing elevated monocytic cytokines.

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.

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.

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.

Effect of neuroleptic administration on serum levels of soluble IL-2 receptor-alpha and IL-1 receptor antagonist in schizophrenic patients

Activation of the inflammatory response system has been reported in schizophrenia. Levels of serum IL-1 receptor antagonist (IL-1ra) and soluble IL-2 receptor (sIL-2R(alpha)) were studied in 32 schizophrenic and 22 age- and sex-matched healthy subjects before and after an 8-week treatment protocol. Psychopathology was assessed with the Positive and Negative Syndrome Scale (PANSS). At weeks 0 and 8, sIL-2R(alpha) levels were significantly higher than in the schizophrenic patients, as well as in a neuroleptic-naive subgroup, than in controls. Patients' sIL-2R(alpha) levels did not vary significantly between weeks 0 and 8. IL-1ra levels in controls did not differ significantly from those in patients at week 0 but were significantly lower at week 8. The patients' serum IL-1ra levels varied significantly between weeks 0 and 8. IL-1ra levels were significantly higher in the subgroup of neuroleptic-naive patients at week 0 than in controls. Levels of sIL-2R(alpha) at week 0 were positively correlated with PANSS positive and negative symptom scores at week 8, and levels at week 8 were positively correlated with PANSS total, positive symptom, and negative symptom scores at week 8. IL-1ra levels at week 0 were positively correlated with PANSS scores at week 8. There were positive correlations between both delta (baseline values minus endline values) IL-1ra and delta sIL-2R(alpha) levels and delta PANSS negative symptoms. The results provide evidence for immune activation in some schizophrenic patients and suggest that medication differentially affects the production of sIL-2R(alpha) and IL-1ra.

ICAM G241A polymorphism and soluble ICAM-1 serum levels: evidence for an active immune process in schizophrenia

OBJECTIVES

We have previously reported reduced serum levels of soluble intercellular adhesion molecule-1 (sICAM-1) in schizophrenic patients. A single-nucleotide polymorphism (SNP) of the ICAM-1 gene was described at position 241. The G-->A SNP results in a nonsynonymous amino acid exchange of the ICAM-1 protein, and the A allele was shown to be also associated with several immunological disorders like rheumatoid arthritis.

METHODS

We investigated 70 schizophrenic patients and 128 unrelated healthy control persons regarding the relationship between the serum levels of sICAM-1 and the ICAM-1 G214A polymorphism.

RESULTS

We were able to replicate our previous finding of reduced sICAM-1 levels in schizophrenia. Healthy control persons carrying the polymorphic A allele showed markedly lower sICAM-1 serum levels than carriers of the homozygous GG wild type (p < 0.004). In contrast, no significant difference in the sICAM-1 serum levels were seen regarding the G241A genotype distribution in schizophrenic patients.

CONCLUSION

We hypothesize that the biochemical effect of the G241A SNP is masked in schizophrenic patients, indicating a disease-related mechanism leading to reduced levels of sICAM-1 in 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.

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.

Immunity and schizophrenia: autoimmunity, cytokines, and immune responses

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

Elevated interleukin-2, interleukin-6 and interleukin-8 serum levels in neuroleptic-free schizophrenia: association with psychopathology

Cytokines have been one of the recent focal points of immunological research in schizophrenia. The present study was to assess the serum levels of some of interleukins in schizophrenia and their relationships with the psychopathological parameters. Seventy physically healthy Chinese patients, who met DSM-III-R criteria for schizophrenia and who were drug-free for at least 2 weeks, were compared with 30 age- and sex-matched Chinese normal controls. The psychopathology of schizophrenia was assessed by the Positive and Negative Syndrome Scale (PANSS). Serum levels of IL-6 and IL-8 were measured by sandwich enzyme-linked immunosorbent assay (ELISA), and serum IL-2 level was assayed by radioimmunometric assay (RIA). Serum levels of IL-2, IL-6 and IL-8 were significantly elevated in patients with a chronic form of schizophrenia (all p<0.05). There was a significant inverse relationship between IL-2 level and the PANSS positive subscale P (r=-0.31, p=0.006) and a significant positive correlation between IL-8 level and PANSS negative subscale N (r=0.25, p=0.036) in schizophrenic patients. In control subjects, a significant and positive relationship between serum IL-2 and IL-6 (r=0.513, p=0.004) was noted, whereas, there was a significant and negative relationship between IL-2 and IL-8 in schizophrenic patients (r=-0.28, p=0.02). Our data confirms and supports the view that immune disturbance is involved in schizophrenia, which is compatible with the possibility that Chinese schizophrenic patients have an ongoing autoimmune process. This immune disturbance is related to the subgroup of schizophrenic patients with characteristic clinical variables. The dysfunction of interaction or inter-adjustment between different cytokines may exist in schizophrenic patients.

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.

Interferon alpha (IFNalpha) and psychiatric syndromes: a review

Interferon alpha (IFNalpha) is used for the treatment of several disorders, such as chronic hepatitis or malignant melanoma. During the therapy, IFNalpha may cause severe neuropsychiatric syndromes including depression with suicidal ideation, paranoid psychoses, or confusional states. The reasons and management of these side effects are widely unknown. Our aim is to review research evidence for the contribution of IFNalpha for the etiopathology of psychiatric syndromes. Therefore, research findings of neuropsychiatric syndromes induced by IFNalpha treatment, the putative mechanisms underlying those syndromes, and their treatment are-reviewed. Furthermore, neuropsychiatric syndromes in diseases with high IFNalpha levels such as systemic lupus erythematosus (SLE) are discussed. Finally, the question is addressed whether IFNalpha may contribute to the etiopathology of endogenous psychiatric disorders. IFNalpha may cause psychiatric syndromes in a subset of treated patients. The underlying pathogenetic mechanisms include various effects on neuroendocrine, cytokine, and neurotransmitter systems. Research data on the role of IFNalpha in the pathogenesis of endogenous psychiatric disorders are conflicting. Future research should improve our understanding of the role of IFNalpha for the etiopathology of psychiatric syndromes and has an impact on treatment of IFNalpha-induced psychiatric syndromes.

Serum interleukin 1 alpha and interleukin 2 levels in patients with schizophrenia

It has been suggested that altered interleukin (IL) regulation may be involved in the pathogenesis of schizophrenia. In this cross-sectional, case-controlled study, patients with schizophrenia and a control group of healthy subjects, matched by age, sex and body mass index, were evaluated. The levels of IL-1 alpha and IL-2 in blood serum were measured by enzyme-linked immunosorbent assay. The fasting serum IL-2 levels were significantly higher in patients with schizophrenia compared with the control subjects, but there was no difference between the fasting serum levels of IL-1 alpha in patients with schizophrenia and the control subjects. Our results suggest that patients with schizophrenia have altered IL-2, but not IL-1 alpha, regulation.

Cytokine profiles in schizophrenic patients treated with risperidone: a 3-month follow-up study

An increasing body of evidence suggests a role for the immune system in the pathogenesis of schizophrenia. The information concerning the effects of antipsychotics on cytokine profiles are limited and often controversial in particular regarding novel antipsychotics. The authors first investigated the production of various cytokines [interleukin (IL)-2, IL-4, IL-10, interferon (INF)-gamma] in drug-free (n = 12) and drug-naive (n = 3) schizophrenic patients and in healthy controls (n = 33) and then the modifications of cytokines values during a 3-month period of treatment with risperidone. In the baseline condition, the production of IL-2 and INF-gamma was significantly higher (P = .023 and .026, respectively) in patients than in controls. In the same patients, the use of risperidone was associated with augmented IL-10 (a suppressor of Type I cytokines) and decreased INF-gamma production. This modification suggests that clinical improvement is associated with a reduction in the inflammatory-like situation present in not currently treated schizophrenic patients.

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.

An abbreviated review of immune abnormalities in schizophrenia

Initial investigations of the possible interaction between schizophrenia and the immune system began in the early 1900s and have proceeded in a rather halting fashion because of the methodological challenges faced by investigators. However, a confluence of recent data suggests that activation of the inflammatory response system, the cellular immune system, and the humoral immune system may be present in some patients with schizophrenia. Some of the most compelling data support the hypothesis that minor levels of immune activation may be associated with acute psychotic exacerbations. However, a second body of evidence suggests that some individuals with schizophrenia may have chronic, evolving autoimmune processes. This article is an overview of the history, rationale, and some of the recent findings on the interaction between schizophrenia and the immune system.

Effects of symptomatic severity on elevation of plasma soluble interleukin-2 receptor in bipolar mania

BACKGROUND

Circulating soluble interleukin-2 receptors (sIL-2Rs) and soluble interleukin-6 receptors (sIL-6Rs) are stable immune measures. Elevated plasma sIL-2R levels are present in patients with schizophrenia, major depression, and bipolar mania, but not with minor psychiatric disorders. The increased plasma sIL-2R levels are state-dependent in bipolar mania. However, altered production of plasma sIL-6R and the effects of clinical characteristics on plasma sIL-6R and sIL-2R levels in bipolar disorder remains uncertain.

METHODS

Plasma sIL-2R and sIL-6R levels were measured in 31 Taiwanese bipolar manic (DSM-IV) patients with Young Mania Rating Scale (YMRS) scores of > or =26 as well as during the subsequent remission (YMRS< or =12), and equal numbers of age- and gender-matched healthy controls. The relationships of clinical variables such as age, age of onset, smoking, medication status, coexisting psychotic features, number of prior episodes, duration of illness, presence of depression before or following the manic episode, and manic severity to plasma sIL-2R and sIL-6R levels in acute mania along with remission were examined.

RESULTS

Plasma sIL-2R but not sIL-6R levels were significantly higher in acute mania than in subsequent remission (P<0.05) and controls (P<0.0005). In acute mania, the plasma sIL-2R levels were significantly correlated to YMRS scores (r=0.34, P<0.05). The remaining clinical variables had no effect on plasma sIL-2R and sIL-6R levels in acute mania or remission. There was a significantly positive relationship between the reduction of plasma sIL-2R levels from the acute to follow-up measurements (DeltasIL-2R) and symptomatic improvement of acute mania (DeltaYMRS) (r=0.61, P<0.001).

LIMITATIONS

Our sample included medicated and unmedicated patients in acute mania. The psychotropic medication may have divergent effects on the plasma sIL-2R levels in acute mania and subsequent remission.

CONCLUSIONS

Elevation of plasma sIL-2R but not sIL-6R levels in bipolar mania supports the idea that the immunomodulatory mechanism may vary in different psychotic disorders. In contrast to being a trait marker in schizophrenia and depressive disorder, plasma sIL-2R levels may be considered a biological indicator of manic severity in a group of bipolar affective patients.

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.

Cytokine profiles in drug-naive schizophrenic patients

A large body of evidence concerning immunological abnormalities in schizophrenic patients seems to suggest a role of the immune system in the multifactorial pathogenesis of schizophrenia. We investigated the production of various cytokines [interleukin (IL)-2, IL-4, IL-10, interferon (INF)-gamma] in drug-free (n=26) and drug-naive (n=7) schizophrenic patients and in healthy controls (n=33). Production of IL-2 and INF-gamma was significantly higher (respectively P=0.021 and P=0.001) in patients than in controls. These findings provide further evidence that immunological abnormalities are present in some schizophrenic patients.

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.

Interferon-gamma (IFN-gamma) levels finally become stable with increasing age as revealed by using an ELISA corresponding to the bioactivity

The immune status is a parameter of the capacity of the immune system to fend off microorganisms. The use of leukocyte subtyping to define the immune status is clinically established. IFN-gamma is a key cytokine directing the immune response. In this study, we investigated whether IFN-gamma is a more sensitive parameter of the immune status. All persons tested showed stable quantities of white blood cell counts over the whole study. Analyses of the lymphocyte subpopulations of two time points resulted in a strong correlation with high statistical significance for the percentage of CD3, CD4, CD8, CD19, CD45 -subtypes and CD56/16 positive cells. IFN-gamma production by the individuals correlates between these time points also, but only if an ELISA strongly correlating to IFN-gamma bioactivity was used instead of other commercial IFN-gamma ELISAs. The IFN-gamma production by males was less variable than by females. Furthermore, intraindividual differences in IFN-gamma secretion were minimal after the age of 46. In conclusion, our data demonstrate that IFN-gamma is a more sensitive parameter for the actual status of the immune system, since its titer shows alterations faster than leukocyte subtyping. Furthermore, leukocyte subtypes do not correspond to the production capacity of the regulatory cytokine IFN-gamma in healthy individuals.

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.

In-vitro immunomodulatory effects of haloperidol and perazine in schizophrenia

There are some reports describing concurrent changes in lymphocytic and monocytic activities in schizophrenia. In this study we investigated T cell activity in schizophrenic patients by measuring the release of interleukin-2 (IL-2) and soluble interleukin-2 receptor (sIL-2R) by T cells and the percentages of CD4+ and CD8+ cells in blood. The release of IL-2 and sIL-2R by T cells was evaluated in dilute whole blood after in-vitro stimulation with phytohemagglutinin. IL-2 levels and the percentage of CD4-cells tended to decrease and sIL-2R levels decreased significantly in schizophrenic patients. Haloperidol and perazine significantly decreased IL-2 levels and increased sIL-2R levels and the percentage CD4-cells. IL-2 and sIL-2R levels were lower in patients with a predominance of positive symptoms. The neuroleptic-induced increase in sIL-2R levels was higher in patients with a predominance of positive symptoms compared with those in whom both positive and negative symptoms were severe. The study has shown that T-cell activity is reduced in schizophrenia and that neuroleptics may have immunomodulatory properties.

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

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

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.

Serum levels of soluble IL-2 receptor alpha, IL-6 and IL-1 receptor antagonist in schizophrenia before and during neuroleptic administration

Serum levels of interleukin-2 soluble receptor alpha (IL-2sR alpha), interleukin-6 (IL-6) and interleukin-1 receptor antagonist (IL-1ra) were determined both before and during neuroleptic administration in an 8-week treatment protocol for schizophrenia. In comparison with a control group, schizophrenia patients showed significantly higher serum levels of IL-2sR alpha, IL-6 and IL-1ra at weeks 0, 1, 4 and 8, and there was a significant negative correlation between the serum level of IL-2sR alpha at week 1 and the age at illness onset. Those of the schizophrenia patients who were neuroleptic-naive had significantly higher pretreatment serum levels of IL-2sR alpha, IL-6 and IL-1ra than the controls. There were significant positive correlations between the IL-2sR alpha levels at weeks 0 and 1, and the psychopathology scores, evaluated using the positive and negative syndrome scale at week 4. IL-6 levels at weeks 0, 1 and 4 were significantly and positively correlated with the duration of illness. The IL-1ra level at week 1 was significantly and positively correlated with positive symptoms at week 1. The present study supports the suggestion that changes in the immune system are involved in the pathophysiology of schizophrenia.

Activation of indices of cell-mediated immunity in bipolar mania

BACKGROUND

Evidence supports that macrophages as well as lymphocytes and their products may be involved in the pathophysiology of psychiatric disorders. Whether patients with bipolar disorder have activation or reduction of immunity during a manic episode remains unclear.

METHODS

The purpose of this case-control study was to investigate the lymphocyte proliferation to phytohemagglutinin (PHA), concanavalin A, and pokeweed mitogen, and plasma levels of soluble interleukin-2 receptor (sIL-2R) and sIL-6R in patients with bipolar mania (DSM-III-R). The subjects were 23 physically healthy patients with Young Mania Rating Scale (YMRS) scores > or = 26 as well as aged < or = 45 years and 23 age- and gender-matched normal control subjects. The above immune variables were measured in acute mania and consequent remission (YMRS scores < or = 12) among bipolar patients.

RESULTS

The lymphocyte proliferation to PHA and the plasma sIL-2R levels, but not sIL-6R, of bipolar patients were significantly higher in acute mania than in consequent remission. These elevations were not due to differences in medication status. Only in acute mania were the plasma sIL-2R levels of patients significantly higher than control subjects. A positive correlation between the changes of manic severity and plasma sIL-2R levels was observed. Remitted bipolar patients and normal control subjects did not differ in any of these measures.

CONCLUSIONS

Cell-mediated immunity activation in bipolar mania was demonstrated and may be through a specifically state-dependent immune response.

Cytokines production in chronic schizophrenia patients with or without paranoid behaviour

1. Several immunological abnormalities have been found in schizophrenia but their significance still remains largely unknown. In this study the authors analyzed mitogen-stimulated interleukin (IL)-2, Interferon gamma (IFN)-gamma and IL-10 (type 2 cytokine) production in a sample of 37 chronic schizophrenic patients as compared with a sample of 40 age and sex-matched controls with the aim to evaluate whether patients belonging to different diagnostic subtypes (i.e. paranoid patients vs non paranoid patients) could be immunologically different from each other. 2. The findings indicate that paranoid patients produce less IL-10 than the others and thus, from an immunological viewpoint, they are more similar to healthy controls. 3. Furthermore, neuroleptic medications were observed to differently affect IL-2 production; this preliminary finding might stimulate further studies aiming to get a link between different drug profile of action both in terms of clinical and receptorial profile and different immunological effects.

Increased serum neopterin levels in acutely ill and recovered schizophrenic patients

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

Psychoneuroimmunology and the cytokine action in the CNS: implications for psychiatric disorders

1. Parallel to the current rapid development of new immunological methods, immune mechanisms are gaining more importance for our understanding of psychiatric disorders. The purpose of this article is to review basic and clinical investigations that elucidate the relationship between the CNS and the immune system. 2. The topical literature dealing with the interactions of immune system, neurotransmitters, psychological processes, and psychiatric disorders, especially in relation to cytokines, is reviewed. 3. An activation of the immune system in schizophrenia and depressive disorders has repeatedly been described. Cytokines, actively transported into the CNS, play a key role in this immune activation. It was recently observed that cytokines activate astrocytes and microglia cells, which in turn produce cytokines by a feedback mechanism. Moreover, they strongly influence the dopaminergic, noradrenergic, and serotonergic neurotransmission. 4. There are indications that the cascade of cytokines can be activated by neuronal processes. These findings close a theoretical gap between stress and its influence on immunity. Psychomotor, sickness behavior and sleep are related to IL-1; disturbances of memory and cognitive impairment are to IL-2, in part also to TNF-alpha. The hypersecretion of IL-2 is assumed to have a prominent influence on schizophrenia, and IL-6, on depressive disorders. 5. Although single cytokines most likely do not have a specificity for certain psychiatric disorders, a characteristic pattern of cytokine actions in the CNS, including influences of the cytokines on the blood-brain barrier, seems to play a role in psychiatric disorders. This may have therapeutic implications for the future.