Immune system abnormalities in schizophrenia include a shift from a Type 1 (cellular) to a Type 2 (humoral) immune response. To characterize the activation status of the immune system in schizophrenia, we examined the pattern of gene expression in peripheral blood cells for three Th1 cytokines (interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2)), and one Th2 cytokine (interleukin-10 (IL-10)). In a cross-sectional study, we used quantitative reverse-transcription polymerase chain reaction (RT-PCR) to compare the mRNA levels of IFN-gamma, TNF-alpha, IL-2, and IL-10 in peripheral blood mononuclear cells (PBMCs) between 15 schizophrenia patients and 15 matched healthy controls. Expression of IFN-gamma and TNF-alpha was significantly reduced in patients with schizophrenia compared with normal controls. No differences in IL-2 and IL-10 gene expression were observed. These results are consistent with impaired Type 1 cellular immunity in schizophrenia. While the data illustrate the potential utility of mRNA-based approaches for the identification and analysis of immune biomarkers for neuropsychiatric disorders, correlation of gene expression with direct measures of cytokine concentrations is required.
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