To determine whether the haplotypes formed on the basis of single-base-exchange polymorphisms at positions -1082, -819, or -592 of the interleukin-10 (IL-10) gene predispose subjects to primary Sjögren's syndrome (SS).
The frequency of IL-10 polymorphisms was analyzed in 62 patients with primary SS and in 400 healthy subjects. These data were assessed for correlations with the concentration of IL-10 in the plasma.
The frequency of the IL-10 GCC haplotype (G at position -1082, C at position -819, and C at position -592 of the IL-10 gene) was increased (P < 0.05, odds ratio [OR] 1.90, 95% confidence interval [95% CI] 0.955-3.62) and the frequency of the ACC haplotype decreased (P < 0.05, OR 0.443, 95% CI 0.257-0.764) in primary SS patients compared with healthy controls. Moreover, the frequency of the ATA haplotype was similar in primary SS patients and healthy controls, but the incidence of the GCC/ATA genotype was elevated in the primary SS patients (P < 0.05, OR 2.19, 95% CI 1.19-4.03). The concentration of plasma IL-10 was significantly higher in patients carrying the GCC haplotype than in non-carriers of GCC.
These results suggest that the presence of the GCC haplotype or the GCC/ATA genotype and the absence of the ACC haplotype of the IL-10 gene are associated with an increased susceptibility to primary SS. This effect is probably mediated by the increased capability to produce IL-10 among carriers of the GCC haplotype.