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 Sjoegren'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 Sjoegren'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 plus or minus 57.5 pg-ml, n = 99) compared with the healthy subjects (9.9 plus or minus 20.3 pg-ml, n = 135, P = 10 super(-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 plus or minus 23.2 pg-ml) as compared with the other two genotype carriers (AA 8.98 plus or minus 16.5 and GA 8.5 plus or minus 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.