The expression of toll-like receptors in peripheral blood mononuclear cells is altered in schizophrenia.

Increasing evidence suggests that in addition to neurochemical abnormalities, various immunological alterations are related to the pathogenesis of schizophrenia. Toll-like receptors (TLRs) actively mediate immune/inflammatory processes and play a pivotal role in damage/danger recognizing. Therefore, the aim of this study was to compare the expression of TLRs in peripheral blood mononuclear cells (PBMCs) in schizophrenic patients with those of healthy subjects. It also measures the metabolic status of the study subjects. Twenty-seven adult European Caucasian patients with paranoid schizophrenia and twenty-nine healthy volunteers were included in this prospective study. qRT-PCR assessed TLR mRNA expression levels. Body composition was measured using two methods: bioimpedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA). The TLR1, TLR2, TLR4, TLR6, and TLR9 expression were down-regulated, in opposite to TLR3 and TLR7 which manifested higher expression in patients with schizophrenia. TLR5 and TLR8 mRNAs did not differ between groups. TLR mRNA expression was highly correlated. Decreased TLR expression may protect against excessive cell stimulation via exogenous and/or endogenous ligands, and may be recognized as a counterbalancing mechanism limiting the excessive development of inflammation.