Mayan alleles of the HLA-DRB1 major histocompatibility complex might contribute to the genetic susceptibility to systemic lupus erythematosus in Mexican patients from Tapachula, Chiapas.

Introduction: Systemic lupus erythematosus (SLE) is the prototypic autoimmune disease that disrupts numerous immunity mechanisms with the potential to exert damage to any organ or tissue. Its etiology remains uncertain; however, genetic and environmental factors that differ between populations strongly influence its development. Among the physiopathogenic factors, the genetic ones predominate, notably the major histocompatibility complex (MHC) loci. A high degree of ethnical admixture makes Mexican Mestizos a thoroughly genetically heterogeneous population. Therefore, this study aimed to identify the MHC polymorphisms associated with SLE development in Mexican Mestizos from Southern Mexico and compare them with patients from Mexico City.

Method: A transversal study in SLE patients from Tapachula, Chiapas, was conducted. DNA typing of human leukocyte antigens (HLA) classes I and II was performed using single specific primers (SSP). Admixture analysis was performed using the population genetics LEADMIX software.

Results: The frequencies of HLA-DRB1*16 and HLA-DQB1*05 were found to have a tendency towards increase in SLE patients, compared to ethnically matched healthy controls. The allele HLA-DRB1*03 seemed to be less associated with SLE in this group of Mexican Mestizos, opposed to other more Caucasian populations. Admixture analysis showed a higher Mayan genetic component in these patients from Chiapas.

Conclusions: The genetic susceptibility for SLE differed in two populations of Mexican Mestizos with dissimilar ethnic ancestries. Autochthonous Amerindian alleles, and not the more widely known Caucasian alleles, might be associated with the susceptibility to SLE in Mexican Mestizos from Tapachula, Chiapas. Key Points • Autochthonous Amerindian alleles, such as HLA-DRB1*16, had a tendency to be increased in SLE patients, compared to healthy controls. • SLE susceptibility alleles vary considerably among regions in Mexico, according to the distribution of the indigenous groups. • Ethnic admixture is a key determinant in the genetic susceptibility of SLE.