Elevated interleukin-2, interleukin-6 and interleukin-8 serum levels in neuroleptic-free schizophrenia: association with psychopathology

Abstract

Cytokines have been one of the recent focal points of immunological research in schizophrenia. The present study was to assess the serum levels of some of interleukins in schizophrenia and their relationships with the psychopathological parameters. Seventy physically healthy Chinese patients, who met DSM-III-R criteria for schizophrenia and who were drug-free for at least 2 weeks, were compared with 30 age- and sex-matched Chinese normal controls. The psychopathology of schizophrenia was assessed by the Positive and Negative Syndrome Scale (PANSS). Serum levels of IL-6 and IL-8 were measured by sandwich enzyme-linked immunosorbent assay (ELISA), and serum IL-2 level was assayed by radioimmunometric assay (RIA). Serum levels of IL-2, IL-6 and IL-8 were significantly elevated in patients with a chronic form of schizophrenia (all p<0.05). There was a significant inverse relationship between IL-2 level and the PANSS positive subscale P ( r=−0.31, p=0.006) and a significant positive correlation between IL-8 level and PANSS negative subscale N ( r=0.25, p=0.036) in schizophrenic patients. In control subjects, a significant and positive relationship between serum IL-2 and IL-6 ( r=0.513, p=0.004) was noted, whereas, there was a significant and negative relationship between IL-2 and IL-8 in schizophrenic patients ( r=−0.28, p=0.02). Our data confirms and supports the view that immune disturbance is involved in schizophrenia, which is compatible with the possibility that Chinese schizophrenic patients have an ongoing autoimmune process. This immune disturbance is related to the subgroup of schizophrenic patients with characteristic clinical variables. The dysfunction of interaction or inter-adjustment between different cytokines may exist in schizophrenic patients.