Altered serum levels of interleukin-3 in first-episode drug-naive and chronic medicated schizophrenia

Elevated serum levels of Interleukin-3 (IL-3), a major component of the cytokines, have been observed in chronic and medicated patients with schizophrenia, but this elevation may reflect either or both medication and illness chronicity effects. Thus, we compared serum IL-3 levels in first-episode drug-naive (FEDN) to chronic medicated patients with schizophrenia and examined the association of IL-3 with their psychopathological symptoms. Serum IL-3 levels were assessed in 55 FEDN patients, 52 chronic medicated patients and 43 healthy controls. Schizophrenia symptomatology was assessed with the Positive and Negative Syndrome Scale (PANSS). Serum IL-3 levels were measured by sandwich enzyme-linked immunosorbent assay (ELISA). We found significantly lower IL-3 levels in FEDN patients than both chronic patients and healthy controls (both p < 0.001), while IL-3 levels in chronic patients were markedly higher than in healthy controls. No significant association was observed between IL-3 and any clinical psychopathology in FEDN patients; however, we found a significant correlation between serum IL-3 levels and the PANSS general psychopathology subscore in chronic medicated patients (p < 0.05). Decreased IL-3 levels in FEDN patients suggest that suppressed immune function may be associated with developing schizophrenia, but as the disease progresses IL-3 levels increase perhaps related to medication treatment or other factors that occur during chronic illness.