HAPLOTYPE DISTRIBUTION OF CLASS-II MHC GENES IN MEXICAN PATIENTS WITHSYSTEMIC LUPUS-ERYTHEMATOSUS

The objective of this project was to determine the association of the DQA10501 allele in the susceptibility to develop systemic lupus eryth ematosus (SLE) in Mexicans. Frequencies of generic MHC Class II genes (HLA-DR, DQA and DQB1) were determined by DNA typing in 58 Mexican mes tizo SLE patients and 96 ethnically matched controls. Statistical anal ysis was performed by chi-square and Fisher's exact tests. The DQA105 01 allele was found to be in linkage disequillibrium with HLA-DR3, DR1 1, and DR14. This explains the lack of association with the allele alo ne, and the evident strong association of SLE with the [HLA-DR3-DQA10 501-DQB10201] and [HLA-DR1-DQA1*0101-DQB1*0501] haplotypes. It was al so found a significant decrease (protection) of the [HLA-DR8-DQA10401 -DQB10402] haplotype which is known to be a characteristic haplotype among the indigenous population of Mexico. These data shows that the s usceptibility to SLE in Mexicans is more strongly influenced by the MH C haplotypes than by single alleles. The suggestion that these genes d o not act alone but in combination, makes the identification of haplot ypes mandatory.