Type-2 Immune Response in Schizophrenia

Several reports described increased serum IL-6 levels in schizophrenia. IL-6 serum levels might be especially high in patients with an unfavourable course of the disease (Muller et al., 2000). IL-6 is a product of activated monocytes and of the activation of the type-2 immune response. Moreover, several other signs of activation of the type-2 immune response are described in schizophrenia, including the increased production ofIgE and an increase ofIL-10 serum levels (Cazzullo et al., 1998 Schwarz et al., 2001). In the cerebrospinal fluid (CSE), IL-10 levels were found to be related to the severity of the psychosis (van Kamnmnen et al., 1997). 

The key cytokine of the type-2 immune response is IL-4. Increased levels of IL-4 in the CSE of juvenile schizophrenic patients have been reported (Mittleman et al., 1997), which supports that the increased type-2 response in schizophrenia is not only a phenomenon of the peripheral immune response. 

Increased R oinflammatory Type-1 Cytokines in Major Depression 

Neopterin is a sensitive marker of the cell-mediated type-1 immunity. The main source of neopterin is monocytes/macrophages. In accordance with the findings of increased monocytes/macrophages, an increased secretion of neopterin has been described by several groups of researchers (Duch et al., 1984 Dunbar et al., 1992 Maes et al., 1994 Bonaccorso et al., 1998). 

The increased plasma concentrations of the proinflammatory cytokines IL-1 and IL-6 observed in depressed patients was found to correlate with the severity of depression and with measures of HEA axis hyperactivity (Maes et al., 1993 Schiepers et al., 2005). As genetics plays a role in MD, the genetics of the immune system in relation to MD has also been investigated. Certain cytokine gene polymorphisms, e.g. 

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