Several studies have shown an involvement of the immune system, in particular the monocytic system, in the pathophysiology of
schizophrenia. Beside others, the monocyte-derived
cytokines TNF-α,
IL-6 and
IL-10 were found to be affected. Since
cytokines are secreted by several different cell types, the cellular source is only clear if intracellular levels are measured. Thus, in order to study the monocytic system in
schizophrenia, the intracellular levels of TNF-α,
IL-6 and
IL-10 were determined. The intracellular concentration of TNF-α,
IL-6 and
IL-10 in CD33 positive monocytes was evaluated in schizophrenic patients and controls with
monoclonal antibodies against these
cytokines. In addition, in vitro stimulation with
lipopolysaccharide (LPS) or
poly I/C, which mimic a bacterial and
viral infection, was performed before immunocytochemistry. At baseline, monocytic
IL-6 levels were significantly lower in schizophrenic patients than in controls. After stimulation with LPS, compared with baseline, monocytic intracellular
IL-6 production tended to increase more in schizophrenic patients. The present results provide further support for the hypothesis of an involvement of a dysfunction of the monocytic system in the pathophysiology of
schizophrenia and indicate that especially the pro-inflammatory immune response seems to be impaired.