HLA-A, -B and -DR Allele and Haplotype Frequencies in the European American, African American, and Hispanic Populations in Dallas, Texas: Relatedness to the North American Population

Dallas is a county located in the U.S state of Texas within the Dallas-Fort Worth-Arlington metropolitan area in north central Texas. As of July 1, 2006, the historic period in Texas including Dallas is defined by the date of contact between aboriginal groups and the Spanish explorers in the 1500s (1). Historical accounts describe that the Dallas area was inhabited by numerous Indian groups before Anglo pioneers began settling in the 1800s. However, archaeologically, Indian groups cannot be found (2). In 1846, the Republic of Texas was annexed by the U.S and Dallas County was established. Dallas has historically been predominantly European American but its population diversified as it grew in size, and Hispanics outnumbered African-Americans for the first time in the 2000 census as the largest minority group in Dallas. The reason for this may be that Dallas is a major destination for Mexican immigrants seeking opportunities in the U.S, because Texas makes up part of the U.S-Mexico border. The current racial makeup of Dallas is 48.3 percent white, 35.5 percent Hispanic (Hispanics may be of any race, so are also included in applicable race categories), 11.3 percent African American, 3.3 percent Asian, 1.0 percent from two or more races, 0.3 percent Native American (American Indian and Alaska Native), 0.2 percent some other race, and 0.1 percent Native Hawaiian and other Pacific Islander according to the census taken in 2006 (3). In the U.S population, several studies focusing on frequencies of HLA antigens and/or alleles and their haplotypes have been reported (4-6). However, HLA alleles and haplotypes in the Dallas, Texas (TX) population have not been reported previously. In the present work, it is intended to obtain the distribution of HLA-A, -B, -DR in the populations of African American, European American, and Hispanic of Dallas, Texas for the first time, in order to estimate gene and haplotype frequencies and compare them with the U.S population. For these purposes, we extracted and presented HLA allele and haplotype frequency data available from the Transplant Donor Program database (TDP) of Southwestern Medical Center at the University of Texas at Dallas from three major U.S. census categories of race and ethnicity. A discriminatory classification of HLA allelic variation on the basis of observed population allele frequencies (very common, common, rare and unseen) based on genotyping for HLA A, B, and DRB1 is introduced. The comparative study of their allele frequencies, characteristic haplotypes and genetic distances with other ABSTRACT