CHARACTERIZATION OF B27 HAPLOTYPES BY OLIGOTYPING AND GENOMIC SEQUENCING IN THE MEXICAN MESTIZO POPULATION WITH ANKYLOSING-SPONDYLITIS - JUVENILE AND ADULT-ONSET

The aim of this study was to investigate the contribution of the diffe rent B27 subtypes in the Mexican Mestizo population with juvenile and adult AS. No differences in the distribution of B27 subtypes were foun d between both populations, B()2705 being the predominant subtype fol lowed by B()2702. Transracial gene mapping was performed in order to find out the origin of the B27 alleles of the Mexican Mestizos. A PCR with SSOPs was used to analyze the polymorphism in exons 2 and 3 of HL A-B27 and HLA-C related alleles. This population shares with the Spani sh Caucasians B()2705 and B(*)2702, which are absent in Central and S outh American Indians. AS and healthy Mexican mestizo donors were anal yzed to ascertain B27/Cw haplotypes. The B27/Cw linkage arrangements s een in mestizos are similar to those reported for Caucasian Spaniards with three different haplotypes positively associated with AS in both populations, B()2705/Cw(*)0102, B(*)2705/Cw(*)02022, and B*2702/ Cw(* )02022, suggesting that B27 in Mexicans may be due to a recent Caucaso id admixture with the Spanish genes. Finally, a strategy for sequence analysis of exons 2 and 3 from genomic DNA of HLA-B27 alleles was deve loped. A novel HLA-BZ7-like allele typed serologically as B27 was iden tified and sequenced by this method in a healthy Mexican mestizo, corr esponding to the B()7301 variant found with low frequency in differen t populations. Analysis of the association of B()7301 to AS would req uire an extensive study in different populations and could provide ins ights into the molecular structure of the alleles involved in the dise ase.