IL‐10 Promoter −1082 Polymorphism is Associated with Elevated IL‐10 Levels in Control Subjects but Does not Explain Elevated Plasma IL‐10 Observed in Sjögren's Syndrome in a Hungarian Cohort

The aim of this study was to investigate the frequency of the −1082 polymorphism of the interleukin‐10 (IL‐10) gene and the soluble IL‐10 levels in Hungarian primary Sjögren's syndrome (SS) patients. Ninety‐nine SS patients and 135 healthy volunteers were examined. Samples were analysed by the PCR restriction fragment length polymorphism method, and IL‐10 plasma levels were assesed by a commercial enzyme‐linked immunosorbent assay. IL‐10 plasma levels were higher in the primary SS patients (36.4 ± 57.5 pg/ml, n = 99) compared with the healthy subjects (9.9 ± 20.3 pg/ml, n = 135, P = 10−6). The elevated IL‐10 phenotype of SS patients was not associated with increased G allele frequency as reported earlier, while in the control group, we found higher IL‐10 levels among the subjects who were carriers of the GG genotype (17.7 ± 23.2 pg/ml) as compared with the other two genotype carriers (AA 8.98 ± 16.5 and GA 8.5 ± 21.1 pg/ml, P = 0.01). Our data do not support previous observations indicating an association between deregulated IL‐10 secretion in SS and higher G allele frequency. However, the results clearly demonstrate that GG homozygosity is associated with elevated IL‐10 levels in apparently healthy subjects, but this cannot account for the IL‐10‐related specific disease features observed in SS. Thus, other genetic factors contribute to the clinical spectrum of this heterogeneous disease at least in the Hungarian population.