In order to investigate human leukocyte antigen (HLA) genes predisposing to primary Sjögren syndrome (pSS), we conducted an association study using HLA loci (A, B, and DRB1) and 9 polymorphic microsatellite markers spanning the HLA region in pSS patients as compared to healthy individuals.
Forty-four patients fitting the European criteria of pSS and 123 healthy controls were analyzed for their HLA class I and class II alleles. HLA class I typing was performed using a standard microlymphocytotoxicity method followed by PCR-SSP. HLA-DRB1 genotyping was performed using PCR-SSP. We studied the polymorphism of 9 microsatellite markers for both groups. Microsatellite genotyping was performed using the PCR fluorescent technique.
We observed a positive association between HLA-B15 and pSS in the Tunisian population (p = 0.004, OR 7.57). The comparison of the frequencies of DRB1 alleles in pSS patients and controls confirmed the association of the DRB1*03 allele with pSS (p = 0.02, OR 2.36). On the other hand, the association study of microsatellite markers showed that the a9 allele of D6S265 marker and the a20 of C1.2.C were found to be positively associated with pSS as compared to controls (p =0.0003, OR 10.29, and p =0.001, OR 4.79, respectively). Using the "Haplo.stats" software analysis, we found that the most associated region was located in the HLA class I region and limited by HLA-A and D6S265 loci (p = 0.00056).
The results of this study support the hypothesis of the existence of a susceptibility gene for pSS located in the HLA class I and III regions.