Th1, Th2 and Th3 cytokine alteration in schizophrenia

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-β1), 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. We recruited 88 schizophrenic patients and 88 matched controls. The basal plasma concentrations of IFN-γ (Th1), IL-4 (Th2) and TGF-β1 (Th3) were studied at the time the patients were admitted to the hospital and following 8 weeks of treatment with antipsychotics. The detection rate of plasma IFN-γ and basal plasma TGF-β1 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-γ/IL-4) was higher in schizophrenic patients. Following the neuroleptic treatment, the IFNγ and TGF-β1 levels returned to control values, and IL-4 concentration rose above the control value. Schizophrenic patients showed higher Th1/Th2 ratio which is attenuated by effective neuroleptic treatment. It is possible that TGF-β1 plays a role in reducing the activity of Th1 cytokine.