The involvement of HLA -DRB1*, DQA1*, DQB1* and complement C4A loci in diagnosing systemic lupus erythematosus among Tunisians.

BACKGROUND

Genetic susceptibility to systemic lupus erythematosus (SLE) varies among populations. Few data exist on associations of HLA class II and class III alleles of the major histocompatibility complex (MHC) and susceptibility to SLE in Tunisians.

PATIENTS AND METHODS

We compared HLA-DRB1*, DQA1, DQB1* and C4 allotypes in 62 Tunisian SLE patients and 100 matched controls. We also assessed the association of specific alleles with distinct autoantibody profiles in SLE patients.

RESULTS

HLA-DRB10301, -DRB11501 and C4AQO alleles were increased in the SLE patients, while the frequencies of HLA-DRB104 and DQB103 were decreased. HLA-DQA10102 and DQA10501 were significantly increased in the SLE patients. HLA-DQB10201 and DQB10602 were more frequent in the SLE patients. C4AQO and C4BQO were increased in frequency in the SLE patients compared to the controls, but only C4A null was significantly increased. Eleven of 17 SLE patients with the C4 null allele were HLA-DRB10301 positive. Three of 16 SLE patients with HLA-DRB11501 were associated with HLA-DQB10501 rather than DQB10602, as has been reported in European SLE patients.

CONCLUSIONS

The MHC class II alleles (DRB1, DQA1, DQB1) and C4 null associations noted in other ethnic groups are also found in Tunisians, suggesting shared susceptibility factors across ethnic lines in predisposition to SLE. In contrast to other ethnic groups, MHC class II alleles are not associated with the presence of specific autoantibodies in Tunisian SLE patients.