An Interleukin-1 receptor antagonist gene polymorphism and a haplotype of the Interleukin-1 gene complex may be associated with schizophrenia
Family, twin and adoption studies demonstrate a strong genetic influence in schizophrenia. The genes encoding for interleukin-1-alpha, beta and receptor-antagonist are in a region on chromosome 2q14, which shows evidence for linkage with schizophrenia. Furthermore, several studies document altered levels of immunological parameters in the blood or CSF of schizophrenic patients. Drug-free schizophrenic patients have been reported to have increased levels of IL-1ß and IL-1RA indicating a possible deregulation of these cytokines.
We analyzed three polymorphisms in the IL-1-gene-complex in schizophrenics and controls. IL-1ß-gene: base exchange polymorphism at position –511; IL-1α-gene: base exchange polymorphism at position –889; IL-1RA gene: variable numbers of 86- base pair tandem repeats in intron 2.
The IL-1RA allele 2 (2 repeats=240 bp) was higher in schizophrenic patients compared to controls. Besides, the number of carriers of a rare haplotype was higher in schizophrenics. These data suggest that the cytokine aberrations in schizophrenia may be partly genetically determined.