and * Alleles Confer a Protective Effect Against ACPA-Positive Rheumatoid Arthritis in a Latin American Admixed Population.

shared epitope (SE) alleles are important genetic contributors for the risk of developing anti-citrullinated protein antibodies (ACPA)-positive rheumatoid arthritis (RA), particularly in Caucasians. We aimed to analyze the contribution of HLA-DRB1 alleles and single nucleotide polymorphisms (SNPs) within the major histocompatibility complex (MHC) region to the susceptibility to develop ACPA-positive RA in a Latin American (LA) population with admixed ancestry. A total of 289 ACPA-positive RA patients and 510 controls were enrolled in this study. The presence of , and was increased in ACPA-positive RA patients compared with healthy controls ( < 0.0001, < 0.001 and < 0.01, respectively), whereas and was associated with a decreased risk of ACPA-positive RA ( < 0.001 and < 0.01, respectively). These results showed a strong correlation with estimates from studies in Asians but not in Caucasian populations. The present study describes the protective effects of the and alleles in ACPA-positive RA patients in a LA population for the first time. Identifying relationships between alleles and RA is important for identifying disease associations in different ethnic groups in order to reach a better understanding of RA worldwide.