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Serum TNF-α, IL-10 and IL-2 in
Schizophrenic Patients Before and After
Treatment with Risperidone and Clozapine
Abolghasem Ajami1, Farshideh Abedian2*, Seyyed Hamzeh Hosseini3, Elahe Akbarian4, Reza Alizadeh-Navaei1, Mehrdad Taghipour5 1Molecular and Cell Biology Research Center, 2Department of Immunology, 3Psychiatry Research Center, 4School of Medicine, Mazandaran University of Medical Sciences, Sari, 5Urology and Nephrology
Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
ABSTRACT
Background: Schizophrenia is a disorder of the executive function of both sensory and
central nervous system. Recent studies suggest that immune mechanisms play a role in
the pathophysiology of this disease. The variations in cytokine concentrations have been
associated with psychopathology and treatment of schizophrenia. Objective: To
investigate the changes in serum concentrations of TNF-α, IL-10, and IL-2 in
schizophrenic patients before and 40 days after treatment. Methods: In a case-control
study, 26 schizophrenic patients and 26 healthy individuals were enrolled as the control
group. PANSS scale questionnaire was used for diagnosis and assessing the severity of
the disease. All patients were then treated with risperidone or clozapine for 40 days.
Serum concentrations of TNF-α, IL-10 and IL-2 were measured by ELISA before and
after treatment in both groups. Paired t-test and Independent t-test were used for
comparison of data. Results: Comparison of TNF-α and IL-10 concentrations in
patients before and after treatment revealed a significance decrease of TNF-α and
increase of IL-10 concentrations (p=0.002, and p=0.008, respectively). Serum
concentrations of IL-2 were lower than the detection limit of assay and were not
detectable. In comparison with healthy controls, serum concentrations of TNF-α in
schizophrenic patients were higher, while IL-10 concentrations were lower before
treatment although the differences were not significant (p=0.291 and p=0.375,
respectively). There was no correlation between cytokine concentrations and the
positive and negative scale (PANSS). Also no significant difference in the admission,
relapses, and duration of illness before and after treatment was observed. Conclusions:
Increase of TNF-α and decrease of IL-10 may have an important role
inpsychopathology of schizophrenia.
Ajami A, et al. Iran J Immunol. 2014; 11(3):200-209
Keywords: Interleukin-2, Interleukin-10, Schizophrenia, Tumor Necrosis Factor alpha
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Corresponding author: Farshideh Abedian, Department of Immunology, School of Medicine, Mazandaran University of
Medical Sciences, Sari, Iran, Tel: (+) 98 11 33543081, Fax: (+) 98 11 33543248, e-mail: [email protected]
Iran.J.Immunol. VOL.11 NO.3 September 2014 200 INTRODUCTION
Schizophrenia is a disorder associated with sensory system and the administrative
function of the central nervous system (CNS) (1). It is one of the most severe mental
injuries that begins at the early-old age and affects men and women with the same ratio.
The prevalence of this disease is about 1% during the longevity of an adult population
and is thought as the most crucial psychiatric disorder (2) with high economical
damage. Total therapeutic and indirect costs of the patients reach about 50 billion
dollars a year. On the other hand, schizophrenia is a chronic disease and affected
patients occupy about 50% of the beds of the mental hospitals.
Antipsychotic drugs are the major treatments for schizophrenia and are divided into two
main groups: 1) dopamine receptor antagonists and 2) antagonists associated with
serotonin and dopamine, but these medications only eliminate the symptoms of the
disorder and do not cure the disease itself (2).
There are various hypotheses about the pathogenesis of this disease, one of which is the
immune system interference (1). Documents suggest that the neural, endocrine, and
immune systems influence each other using cytokines, hormones, and neurotransmitters
(3). Activation of the immune system causes fever and behavioral, neuroendocrine and
neuropathologic changes in the CNS (4). These changes efficiently occur by the
interaction of cytokines with their receptors on the neurons and the glial cells in the
brain (5).
Cytokines are proteins secreted by different cells and perform paracrine, endocrine and
even autocrine functions. They can relatively penetrate into the blood-brain barrier and
bind to their receptors on the neurons and glial cells (6). Furthermore, cytokines have
the capacity to be produced inside the CNS. Although many cytokines are secreted by
the glial cells in the brain, some documents reveal that cytokines could also be produced
by the neurons under specific conditions (7).
The involvement of cytokines produced by the microglia, astrocytes, neurons, and
endothelial cells in the pathogenesis of different psychiatric disorders, like
schizophrenia, acute depression, panic disorders and autism, have been widely surveyed
(8). On the other hand, the expression of the cytokines in the CNS refers to the role of
this intercellular messenger in different physiologic processes such as CNS
differentiation (9), synaptic transmission (10), cognition (11), regulation of the
hypothalamus-hypophysis axis (HPA) (12), dream (13), and appetite (14).
There is some evidence that supports the cytokine changes in the schizophrenia and
acknowledges the effect of antipsychotic drugs in the regulation of these changes
(15,16); however, there are many controversies in different studies. Theodoropoulou et
al. reported the increased concentrations of TNF-α in schizophreniac patients (17)
compared to the control group, while others reported a decrease in TNF-α
concentrations (18) or even normal concentrations of TNF-α (19). There are studies
showing increased concentrations of TNF-α in treated cases compared to the control
group (20,21), whereas others reported the decreased concentrations of TNF-α in
treated patients (22,23). These controversial results have also been observed in studies
measuring other cytokines such as IL-10 and IL-2. Regarding IL-10, Kaminska et al.
(24) and Obrien et al. (25) demonstrated decrease of IL-10, whereas Chang et al. (26)
and Kunz et al. (27) reported increase of IL-10, and Kubistova et al. demonstrated the
normal amount of IL-10 in schizophrenic patients (28). Also, Zhang et al., revealed
Iran.J.Immunol. VOL.11 NO.3 September 2014 Increased TNF-α in schizophrenia increase of IL-2 while Manderan et al. (16) and Theodoropoulou et al. (17) reported
decrease of IL-2 in this diseases.
In this study, the serum concentrations of TNF-α, IL-2, and IL-10 as innate, adaptive,
and regulatory cytokines were measured in patients with schizophrenia before and after
treatment and compared with the control group to reveal the probable role of these
cytokines in the pathogenesis of schizophrenia.

MATERIALS AND METHODS
Inclusion Criteria. A case-control study was conducted in patients who referred to the
Zare Hospital, Sari, Iran, with a diagnosis of schizophrenia during July 2008 to January
2011. The diagnosis was confirmed by administration of interviews such as SCID
(Structured Clinical Interview for DSM-IV). All patients were asked to complete a
written consent form, before entering the study. Also the project was approved by the
Ethics Committee of Mazandaran Medical University. Patients who were diagnosed for
the first time or individuals whose disease relapsed due to the lack of compliance to
therapy and the physician had used second-generation antipsychotic drugs for their
treatment, enrolled in the study.
Subjects. Thirty patients who had the eligibility criteria were selected for this study.
Due to the lack of enough serum samples of the second sampling stage, four patients
were excluded and finally the results of 26 patients were analyzed. Those patients who
had used drugs in addition to second-generation medications or suffered from other
psychiatric disorders were also excluded. 26 individuals were also selected as controls.
Individuals in the control group were blood donors who referred to the blood
transfusion organization Sari, Iran and had no history of antipsychotic drug taking and
no past history of any psychiatric disorders. These individuals were age and sex
matched with the cases and had normal CRP and ESR levels.
Data Collection Sampling and Treatment. Data were collected by using two
questionnaires for evaluating the schizophrenic symptoms, demographic features, and
also the medication history. An International PANSS questionnaire (29) was used to
assess positive and negative symptoms in patients. After confirming the diagnosis of
schizophrenia in patients, the treatment with risperidone and clozapine was initiated
based on the patient's condition. Clozapine was used when their previous treatments had
not been successful or when the treatments had caused adverse side effects. Moreover,
risperidone was administered once or twice daily in other cases. Before the treatment 5
ml of venous blood was taken and serum was isolated. All samplings were conducted
during the morning hours. The sera were immediately sent to a central laboratory and
stored in -70°C degrees. Sampling was repeated 40 days after the start of treatment.
Five milliliters of venous blood was also taken from each individual of the control
group and the serum was separated in the same conditions as the case group.
ELISA Assay. Serum concentrations of TNF-α, IL-10, and IL-2 were measured using
commercial ELISA kits (Avibion, Finland) according to the manufacturer's instructions.
Laboratory experiments were done in a blind format where the information about the
samples was not revealed until the time of analysis.
Statistical Analysis. Data was analyzed using SPSS 18.0 software (SPSS, Chicago, IL,
USA). Serum concentrations of cytokines in patients before treatment and forty days
after onset, and also changes in PANSS scale data were compared using paired-t-test.
Iran.J.Immunol. VOL.11 NO.3 September 2014 Pearson test was used to determine the correlation between serum concentrations of
cytokines before and after treatment. Spearman test was used for evaluating the
relationship between cytokines concentrations and PANSS scale. The independent t-test
was used for examining the relationship between disease relapse, times of
hospitalization, disease duration with cytokines concentrations and also for
differentiating the efficacy of the clozapine and risperidone on cytokine concentrations.
P values less than 0.05 were considered statistically significant.

RESULTS

Of 52 subjects who participated in the study, 26 patients belonged to the case group and
26 belonged to the control group. Patients and controls were matched for age and sex.
The mean ages of the case and control groups were 33.62 ± 9.49 yrs and 33.92 ± 8.86
yrs, respectively. In total, 40 (76.92%) participants were male and 12 (23.08%) were
female. An international PANSS questionnaire was used for detecting positive and
negative symptoms of schizophrenic patients and to assess the response to treatment in
this study. The mean scores of the evaluated variables in this questionnaire are
mentioned in Table 1.
Table 1. Mean scores of positive and negative symptoms before and after the
treatment.

PANSS Questionnaire Scores
Before the Treatment
After the Treatment
Mean total score Mean of positive symptom scores Mean of negative symptom scores Serum concentrations of the TNF-α, IL-10, and IL-2 were measured in schizophrenia patients before and after treatment and compared by paired t-test (Table 2). Concentration of these cytokines were also measured in sera of healthy control group and compared with patients by t-test (Table 2). Results showed statistical significant changes between concentrations of TNF-α and IL-10 in the case group before and after treatment. However, serum concentrations of IL-2 in all case and control groups were less than the sensitivity of the assay, and therefore, IL-2 was not detectable in sera of schizophrenia patients as well as the control group. In other words, we could say that the concentration of the IL-2 in the schizophrenia patients were not increased and were the same as the control group. Iran.J.Immunol. VOL.11 NO.3 September 2014 Increased TNF-α in schizophrenia
Table 2. Serum concentrations of cytokines in patients (before and after
treatment) and in control group.

Concentration before treatment
Concentration after treatment
Case Control Case
Lesser than kite *The provided P-value shows the differences between serum concentrations of cytokine in case group before and after treatment, not between case and control group. The comparison of the serum concentrations of the TNF-α and IL-10 before and after
treatment declare the significant decrease in TNF-α in the treated schizophrenia
patients, (p=0.002; Figure 1) while IL-10 increases after treatment (p=0.008; Figure 2).
The comparison of the serum concentrations of the cytokines before treatment with the
control group demonstrated that the serum concentrations of TNF-α in the schizophrenia
patients is more than healthy control (p=0.291) but serum concentrations of the IL-10 is
less in the control group (p=0.375).

Figure 1. Serum concentrations of TNF-α in patients (before and after treatment) and in control
group.
Iran.J.Immunol. VOL.11 NO.3 September 2014

Figure 2. Serum concentrations of IL-10 in patients (before and after treatment) and in control
group.

Of 26 Patients treated with second generation of antipsychotic drugs, 16 patients treated
with the risperidone and 10 individuals treated with the clozapine. To investigate the
comparative effects of the above drugs on the level of TNF-α and IL-10, the
independent samples t-test was used. Although the treatment caused a significant
decrease in the serum concentrations of TNF-α and an increase in IL-10 concentration,
the comparison of the effect of these two drugs did not demonstrate any significant
difference. In other words, although risperidone has more decreasing effect on TNF-α
level and more increasing effect on IL-10 than clozapine, the differences did not reach
the significant level.
To investigate the relation between the frequency of hospital admissions, frequency of
relapses and the duration of the illness with the concentration of the TNF-α and IL-10
Pearson Correlation Test was used. Results showed that there was no relation between
the frequency of hospital admissions, frequency of relapses and the duration of the
illness with the concentrations of the TNF-α and IL-10.
PANSS score in schizophrenia patients were analyzed by Spearman test to evaluate the
relationship between cytokines concentrations and symptom scores (total, positive, and
negative scores). There was no significant relation between the scores of PANSS
questionnaire and the serum concentrations of the TNF-α and IL-10, before and after the
treatment.

DISCUSSION
In this study, the serum concentration of TNF-α in the patients with schizophrenia was
higher than the control group. After treatment, however, it was decreased to normal
concentrations similar to that of the control group. This was in agreement with the data
Iran.J.Immunol. VOL.11 NO.3 September 2014 Increased TNF-α in schizophrenia given by Monteleone et al. following ten weeks (22) and Kim et al. following six weeks of treatment (23). Also, Dunjic-Kostic et al. indicated decreased concentrations of TNF-α during acute and remission phase (18). Other studies showed increased serum concentrations of TNF-α after four to six weeks of treatment (17,20,21,28,30) or no change in its concentrations (19,24,27). TNF-α is a pro-inflammatory cytokine, which is increased in innate immune responses and also during Th1 and Th17 activation. It may also takes part in the pathogenesis of schizophrenia by activating the Hypothalamo-Pituitary-Adrenocortical (HPA) axis, activating-secretion of serotonin as a neurotransmitter and stimulating the indoleamine 2-3-dioxygenase which leads to elimination of tryptophan and activation of kynurenine metabolites, or releasing of the neurotoxic glutamic acid (31). In this study, serum concentrations of IL-10 in the schizophrenic patients showed decline in comparison with the control group and increase in the patients under treatment. Studies of Kaminska et al. (24) and Obrien et al. (25) showed decline of IL-10 in the schizophrenic patients, while data given by Chang et al. (26) and Kunz et al. (27) indicated increased serum concentrations of IL-10. However, Kubistova et al. (28) reported no change of this cytokine in schizophrenia. Considering the anti-inflammatory properties of IL-10, which could prevent the release of pro-inflammatory cytokines such as TNF-α, decreased serum concentrations of IL-10 in the schizophrenic patients indicates the lack of regulatory activities of immune system that could help in increased TNF-α levels and its effects. In this study, serum concentrations of IL-2 in the case and control groups was very low and was not measurable by our assay, suggesting no change in IL-2 concentration in sera from schizophrenic patients. Hence, we can assume that endocrine IL-2 has no effect on schizophrenic pathogenesis. Data given by Manderan et al. (16) and Theodoropoulou et al. (17) showed decrease of serum concentrations IL-2 while that of Zhang et al. (23) revealed increase of this cytokine. Various data given by different authors regarding the serum concentrations of cytokines in the schizophrenic patients are controversial which could be due to the differences in the cytokine measuring techniques or in the type of samples being tested (serum, plasma, or CSF), small sample sizes, sampling during different phases of the disease (acute, chronic, active phase, or remission), types of antipsychotic drugs and treatment responsiveness (32). Two studies by Haack et al. 32 and Singh et al. (33) showed that patients' characteristics such as age, sex, smoking, body mass index (BMI), infectious diseases, and the previous non-systematic treatment could affect the serum concentrations of cytokines. One study indicated the increase of TNF-α in the schizophrenic patients even after treatment and they related this increase to silent toxoplasmosis, which is two to three times more prevalent in schizophrenic patients (34,35). In this study, we tried to control the confiding variables to obtain more accurate results. Therefore, we included patients with normal concentrations of CRP and RF to exclude any infection and inflammation. Also, we only included patients under treatment with the second generation of antipsychotic drugs, and the severity and response to treatment in schizophrenic patients was evaluated through measuring of PANSS. Our data shows no significant relationship between serum concentrations of IL-10 and TNF-α prior to and after treatment, using the PANSS questionnaire (total, positive, and negative symptoms). Kubiostova et al. (33) indicated no significant association between serum concentrations of IL-10 and TNF-α using the PANSS questionnaire which is in agreement with our findings. Iran.J.Immunol. VOL.11 NO.3 September 2014 In this study, after 40 days of treatment with risperidone and clozapine the serum
concentrations of IL-10 and TNF-α were determined. It was found that, both types of
the drugs used, had effect on treatment of diseases (PANSS score) and increase or
decrease of these cytokines. Although risperidone has more effects on the mean
concentrations of these cytokines compared to the clozapine, there was no significant
difference between these two drugs in treatment effect and cytokine concentrations.
In the present study, no significant relationship was observed between frequency of
hospital admission, relapse and duration times of illness with the serum concentrations
of TNF-α and IL-10 prior to and after the treatment. Few studies have been conducted
to determine the relationship between these factors and serum concentrations of
cytokine.
One limitation of the present study was measuring of cytokines in the serum. Since most
biological activities of cytokines is exerted in the paracrine and autocrine modes, it
would have been more accurate to measure them locally in the CNS of age/sex
matching groups and include patients treated with one type of antipsychotic drugs which
then could give more credible results.
In conclusion, our data showed that increase of TNF-α and decrease of IL-10 might
have an important role in the psychopathology of schizophrenia, as we showed an
increase in serum levels of TNF-α in contrast to a low level of IL-10 in patients with
schizophrenia. Therefore, decrease and increase in cytokine serum levels in health and
disease may be attributed to host and environmental factors. A further investigation is
needed to explore if the increase and decrease in serum levels of TNF-α, IL-10 are
directly related to the etiology of schizophrenia.

ACKNOWLEDGEMENTS
This work was financially supported by Mazandaran University of Medical Sciences
(MAZUMS). Also thanks to the laboratory staff of Zare Hospital for blood sampling
and Dr. Fazlali and Dr. Nazemi (Residents of psychiatrics) for helping in data
collection. Special thanks to Ms. Mina Rostami, Dr. Mehran Taghipour and Dr. Sovaid
Taghipour for their critical reading of the manuscript.

REFERENCES

Vogel M, Busse S, Freyberger HJ, Grabe HJ. Dopamine D3 receptor and schizophrenia: a widened scope for the immune hypothesis. Medical hypotheses. 2006; 67:354-8. Sadock Bj, A SV. pocket handbook of clinical psychiatry. philadelphia: Lippincott Williams and Wilkins; 2005:117-9 Masek K, Slansky J, Petrovicky P, Hadden JW. Neuroendocrine immune interactions in health and disease. Int Immunopharmacol. 2003; 3:1235-46. Reale M, Patruno A, De Lutiis MA, Pesce M, Felaco M, Di Giannantonio M, et al. Dysregulation of chemo-cytokine production in schizophrenic patients versus healthy controls. BMC Neurosci. 2011; 12:13. Sawada M, Itoh Y, Suzumura A, Marunouchi T. Expression of cytokine receptors in cultured neuronal and glial cells. Neurosci Lett. 1993; 160:131-4. Yarlagadda A, Hampe CS, Clayton AH. The blood brain barrier and the role of ratiometric molecular analysis in schizophrenia. Psychiatry (Edgmont). 2010; 7:20-3. Freidin M, Bennett MV, Kessler JA. Cultured sympathetic neurons synthesize and release the cytokine interleukin 1 beta. Proc Natl Acad Sci USA. 1992; 89:10440-3. Iran.J.Immunol. VOL.11 NO.3 September 2014 Increased TNF-α in schizophrenia Sredni-Kenigsbuch D. TH1/TH2 cytokines in the central nervous system. Int J Neurosci. 2002;m 112:665-703. Taga T, Fukuda S. Role of IL-6 in the neural stem cell differentiation. Clinl Rev Allergy Immunol. 2005; 28:249-56. Petitto JM, McCarthy DB, Rinker CM, Huang Z, Getty T. Modulation of behavioral and neurochemical measures of forebrain dopamine function in mice by species-specific interleukin-2. J Neuroimmunol. 1997; 73:183-90. Wilson CJ, Finch CE, Cohen HJ. Cytokines and cognition--the case for a head-to-toe inflammatory paradigm. J Am Geriatr Soc. 2002; 50:2041-56. Turnbull AV, Rivier CL. Regulation of the hypothalamic-pituitary-adrenal axis by cytokines: actions and mechanisms of action. Physiol Rev. 1999; 79:1-71. Opp MR. Cytokines and sleep. Sleep Med Rev. 2005; 9:355-64. Hori T, Nakashima T, Take S, Kaizuka Y, Mori T, Katafuchi T. Immune cytokines and regulation of body temperature, food intake and cellular immunity. Brain Res Bull. 1991; 27:309-13. Na KS, Kim YK. Monocytic, Th1 and th2 cytokine alterations in the pathophysiology of schizophrenia. Neuropsychobiology. 2007; 56:55-63. Mahendran R, Mahendran R, Chan YH. Interleukin-2 levels in chronic schizophrenia patients. Ann Acad Med Singapore. 2004; 33:320-3. Theodoropoulou S, Spanakos G, Baxevanis CN, Economou M, Gritzapis AD, Papamichail MP, et al. Cytokine serum levels, autologous mixed lymphocyte reaction and surface marker analysis in never medicated and chronically medicated schizophrenic patients. Schizophrenia research. 2001; 47:13-25. Dunjic-Kostic B, Jasovic-Gasic M, Ivkovic M, Radonjic NV, Pantovic M, Damjanovic A, et al. Serum levels of interleukin-6 and tumor necrosis factor-alpha in exacerbation and remission phase of schizophrenia. Psychiatria Danubina. 2013; 25:55-61. Erbagci AB, Herken H, Koyluoglu O, Yilmaz N, Tarakcioglu M. Serum IL-1beta, sIL-2R, IL-6, IL-8 and TNF-alpha in schizophrenic patients, relation with symptomatology and responsiveness to risperidone treatment. Mediators inflamm. 2001; 10:109-15. Hinze-Selch D, Mullington J, Pollmacher T. [Clozapine, cytokines, fever and sleep]. Wien Med Wochenschr. 1996; 146:311-3. Pollmacher T, Hinze-Selch D, Mullington J. Effects of clozapine on plasma cytokine and soluble cytokine receptor levels. J Clin Psychopharmacol. 1996; 16:403-9. Monteleone P, Fabrazzo M, Tortorella A, Maj M. Plasma levels of interleukin-6 and tumor necrosis factor alpha in chronic schizophrenia: effects of clozapine treatment. Psychiatry research. 1997; 71:11-7. Kim YK, Myint AM, Verkerk R, Scharpe S, Steinbusch H, Leonard B. Cytokine changes and tryptophan metabolites in medication-naive and medication-free schizophrenic patients. Neuropsychobiology. 2009; 59:123-9. Kaminska T, Wysocka A, Marmurowska-Michalowska H, Dubas-Slemp H, Kandefer-Szerszen M. Investigation of serum cytokine levels and cytokine production in whole blood cultures of paranoid schizophrenic patients. Archivum immunologiae et therapiae experimentalis. 2001; 49:439-45. O'Brien SM, Scully P, Dinan TG. Increased tumor necrosis factor-alpha concentrations with interleukin-4 concentrations in exacerbations of schizophrenia. Psychiatry Res. 2008; 160:256-62. Chang SH, Chiang SY, Chiu CC, Tsai CC, Tsai HH, Huang CY, et al. Expression of anti-cardiolipin antibodies and inflammatory associated factors in patients with schizophrenia. Psychiatry research. 2011; 187:341-6. Kunz M, Cereser KM, Goi PD, Fries GR, Teixeira AL, Fernandes BS, et al. Serum levels of IL-6, IL-10 and TNF-alpha in patients with bipolar disorder and schizophrenia: differences in pro- and anti-inflammatory balance. Rev Bras Psiquiatr. 2011; 33:268-74. Kubistova A, Horacek J, Novak T. Increased interleukin-6 and tumor necrosis factor alpha in first episode schizophrenia patients versus healthy controls. Psychiatria Danubina. 2012;24 :153-6. Emsley R, Rabinowitz J, Torreman M, RIS-INT-35 Early Psychosis Global Working Group. The factor structure for the Positive and Negative Syndrome Scale (PANSS) in recent-onset psychosis. Schizophr Res. 2003; 61:47-57. Lin CC, Chang CM, Chang PY, Huang TL. Increased interleukin-6 level in Taiwanese schizophrenic patients. Chang Gung Med J. 2011; 34:375-81. Iran.J.Immunol. VOL.11 NO.3 September 2014 Himmerich H, Berthold-Losleben M, Pollmacher T. [The relevance of the TNF-alpha system in psychiatric disorders]. Fortschritte der Neurologie-Psychiatrie. 2009;77:334-45. Haack M, Hinze-Selch D, Fenzel T, Kraus T, Kuhn M, Schuld A, et al. Plasma levels of cytokines and soluble cytokine receptors in psychiatric patients upon hospital admission: effects of confounding factors and diagnosis. Journal of psychiatric research. 1999;33:407-18. Singh B, Bera NK, Nayak CR, Chaudhuri TK. Decreased serum levels of interleukin-2 and interleukin-6 in Indian Bengalee schizophrenic patients. Cytokine. 2009; 47:1-5. Beaman MH, Hunter CA, Remington JS. Enhancement of intracellular replication of Toxoplasma gondii by IL-6. Interactions with IFN-gamma and TNF-alpha. J Immunol. 1994; 153:4583-7. Horacek J, Flegr J, Tintera J, Verebova K, Spaniel F, Novak T, et al. Latent toxoplasmosis reduces gray matter density in schizophrenia but not in controls: voxel-based-morphometry (VBM) study. The world journal of biological psychiatry : the official journal of the World Federation of Societies of Biological Psychiatry. 2012;13:501-9. Iran.J.Immunol. VOL.11 NO.3 September 2014

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