Soluble interleukin 2 receptor levels in families of people with schizophrenia

Background: Several authors have reported increased soluble interleukin 2 receptor (sIL2Rα) concentrations in schizophrenia. The aim of this work was to examine serum sIL2Rα in the first degree relatives of patients with schizophrenia. Methods: We sampled 51 first degree relatives of patients with DSM IIIR schizophrenia. These relatives were unaffected by psychosis and included nine fathers, thirteen mothers, seventeen sisters and twelve brothers. They were compared to 126 controls who were not pregnant, had no known autoimmune disorder and no intercurrent illness. Neither the controls, nor their first degree relatives, suffered from a psychotic illness. Serum sIL2Rα was analysed using a commercial ELISA preparation (Quantikine sIL2Rα immunoassay - R and D Systems, Inc.). We used non-parametric Mann Whitney U test and Spearman correlation throughout. SIL2Rα levels were adjusted for higher levels in females and with increasing age. Results: Adjusted mean sIL2Rα values of unaffected siblings, averaged within their families, were higher than controls (n=14, one-tailed p=0.027). There was no difference in sIL2Rα values between fathers or mothers and controls following regression for age and sex. Conclusion: Soluble interleukin 2 receptorα levels are increased in siblings of patients with schizophrenia.