Interferon responses in schizophrenia and major depressive disorders

The spontaneous and induced interferon (IFN) production in whole blood cultures was examined in 45 psychiatric inpatients and in 65 normal controls. Among inpatients there were 32 who were chronic schizophrenics (14 women, 18 men) and 13 who were severely depressed (11 women, 2 men). The analysis of the pooled results of assays in the heterogeneous population showed that leukocytes of the psychiatric patients produced significantly lower levels of IFN after stimulation with virus (NDV), lipopolysaccharide (LPS), and IFN spontaneously released without the inducers that control cells. In contrast, there was no difference between the psychiatric patients and controls in IFN response to phytohemagglutinin and phorbol myristate acetate (PHA + PMA). The results apparently confirmed observations made by Moises et al (1985) and Katila et al (1989). We have also tested our hypothesis that the statistics may mask the individual pattern of IFN response related to the specific psychiatric diagnosis, however. In fact, in the group of chronic schizophrenics we have found either high or low responders to all IFN inducers (NDV, PHA + PMA and LPS). Furthermore, the patients with high IFN response had dominant positive symptoms of schizophrenia (delusions, hallucinations, bizarre behavior and thought disorder). Whereas, in the patients with low IFN response the negative symptoms prevailed (asociality or withdrawal, flat affect, attention impairment, abolition or apathy). In plasma samples of schizophrenics, factors were detected that transferred a hypersensitivity to the IFN inducers to normal donor leukocytes. For instance, in leukocytes cultured in the presence of plasma from schizophrenics, there were 71% of high IFN responders after stimulation with NDV, versus 26% of high IFN responders in the presence of plasma from normal controls. We suggest that the factors may belong to the class of opioid peptides, which interact with the production of cytokines including IFNs.