Mitogen-stimulated interleukin-2 production in never-medicated, first-episode schizophrenic patients. The influence of age at onset and negative symptoms.

BACKGROUND: Decreased interleukin-2 (IL-2) production is characteristic of active autoimmune diseases and has previously been reported in patients with schizophrenia. We attempted to replicate this finding in never-medicated schizophrenic patients and examine the possible correlation between IL-2 production and clinical variables.
METHODS: The production of IL-2 was measured in equal numbers (N = 33) of DSM-III-R-diagnosed schizophrenic patients and controls who were matched for age, race, and gender. Patients were also assessed for positive, negative, and depressive symptoms.
RESULTS: The production of IL-2 was significantly lower in patients than in controls. There was a significant positive correlation between IL-2 production and age at onset, and significant negative correlation between IL-2 production and negative symptom scores. In multivariate analyses, the predictive power was stronger for age at onset than for negative symptoms. Positive or depressive symptoms were unrelated to IL-2 production.
CONCLUSIONS: Our finding of low IL-2 production in neuroleptic-native schizophrenic patients confirms that this finding is not confounded by medications. The correlation of low IL-2 production with younger age at onset suggests that this may be a marker for a subtype of the illness or for severity.