Background: Several authors have reported increased soluble interleukin 2 receptor (sIL2Ralpha) concentrations in schizophrenia. The aim of this work was to examine serum sIL2Ralpha 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 sIL2Ralpha was analysed using a commercial ELISA preparation (Quantikine sIL2Ralpha immunoassay - R and D Systems, Inc.). We used non-parametric Mann Whitney U test and Spearman correlation throughout. SIL2Ralpha levels were adjusted for higher levels in females and with increasing age.
Results: Adjusted mean sIL2Ralpha values of unaffected siblings, averaged within their families, were higher than controls (n=14, one-tailed p=0.027). There was no difference in sIL2Ralpha values between fathers or mothers and controls following regression for age and sex.
Conclusion: Soluble interleukin 2 receptoralpha levels are increased in siblings of patients with schizophrenia.