HLA frequencies in a Mexican American population.

HLA-A and -B antigens were determined for 300 unrelated Mexican-Americans and 300 unrelated Caucasians from San Antonio by the microlymphocytotoxicity technique, using lymphocytes isolated from freshly drawn peripheral blood. Haplotype frequencies for the Mexican American population were obtained directly, based on family studies, as well as estimated from phenotype data. The results revealed clear differences in the distribution of HLA antigens between Mexican American and Caucasian populations. The predominant HLA specificities in Mexican Americans were A2 and Bw35, while the most frequently observed haplotypes were A2-Bw35, A2-B12 and A2Bw40. Despite the distinct differences in HLA antigen distribution between Mexican American and Caucasian populations, genetic distance values, calculated from the HLA frequencies, were surprisingly low.