We discuss the role of immune system disturbance in schizophrenia and especially changes of serum levels of cytokines in patients with schizophrenia. The cytokines are essential to wide range of functions related to the defense of the organisms from infectious and environmental dangers. However it is not known whether cytokines influence the presentation of psychotic symptoms. Identification of changes in the serum level of certain cytokines and their correlation with distinct psychopathological symptoms may facilitate the identification of subgroups of patients who are likely to benefit from immunotherapy or anti-inflammatory therapy. Such patients may benefit from tailored immunotherapy designed for modulation of abnormal cytokine levels related to specific positive or negative symptoms of schizophrenia. 1. Introduction Accumulating evidence supports the view that immunological dysfunction may have a role in the etiology of psychotic disorders. In a recent publication in Nature by the Schizophrenia Working Group of the Psychiatric Genomic Consortium were identified 108 schizophrenia associated loci [1]. Notable associations with the dopaminergic and glutaminergic neurotransmitters as well as associations with voltage gated calcium channels subunits were found. The most significant association was with the major histocompatibility complex and with a region involved in acquired immunity. A recent study provides encouraging evidence that biological signatures for schizophrenia can be identified in blood serum [2]. The role of the immune system disturbance was recently reviewed [3]. An important role leading to these changes is played by the cytokines [4, 5]. Cytokines are low-molecular weight proteins secreted by immune cells and other cell types in response to a number of environmental stimuli, particularly infections. They have wide-ranging roles in the innate and adaptive immune systems, where they help regulate the recruitment and activation of lymphocytes as well as immune cell differentiation and homeostasis. In addition, some cytokines possess direct effector mechanisms, including induction of cell apoptosis and inhibition of protein synthesis. Previously we described dysregulated production of cytokines and their association with psychopathology of schizophrenia as well as the possible involvement of the Th17/IL-17 pathway [6, 7]. We found significantly increased levels of GRO, MCP-1, MDC, and sCD40L and significantly decreased levels of IFN-γ, IL-2, IL12-p70, and IL-17. In addition, we observed positive correlations between levels of cytokines
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