HLA polymorphism and evaluation of European, African, and Amerindian contribution to the white and mulatto populations from Parana, Brazil

Human Biology, Aug 2000 by Probst, C M, Bompeixe, E P, Pereira, N F, de O Dalalio, M M, Et al

Results

A homogeneity test was used to evaluate the significance of differences among subsamples from several geographic regions of Parana. Since no significant difference was seen, the data were analyzed as a whole.

Antigen and Allele Frequencies. Frequencies of HLA-A, -B, -C, -DR and -DQ antigens and alleles are listed in Table 2. In the white sample, the 3 most frequent specificities for each locus are: for HLA-A, A2, A24(9) and A3; for HLA-B, B35, B51(5) and B44(12); for HLA-C, Cw7, Cw4 and Cw3; for HLA-DR, DR11(5), DR4 and DR7; and for HLA-DQ, DQI, DQ7(3) and DQ2. These antigens are common in Europeans, such as Portuguese (Carvalho 1983; Imanishi et al. 1992a), Italian (Piazza et al. 1989; Imanishi et al. 1992a), German (Imanishi et al. 1992a), and others, and in several Latin-- American admixed populations that are of predominantly European origin (Sierp et al. 1987; Trachtenberg et al. 1988; Imanishi et al. 1992a; Rosales et al. 1992; Alvarez et al. 1993) or have Europeans as important contributors (Arellano et al. 1981; Chauvenet et al. 1981). The most common antigens in the mulatto sample are: for HLA-A, A2, A3 and A30(19); for HLA-B, B35, B44(12) and B7; for HLA-C, Cw4, Cw3 and Cw7; for HLA-DR, DR7, DR6 and DR15(2); for HLA-DQ, DQ1, DQ2 and DQ3 other than DQ7(3). The HLA antigen frequencies in the mulatto sample are mostly intermediate between European and African frequencies, as expected. There are significant differences between the 2 samples regarding frequencies of the following antigens: A2, A25(10), A30(19), B51(5), B12, B42, B53, DR15(2), DR4, DR11(5), DR12(5), DR6 and DQ7(3). Most of these antigens present great differences between European and sub-Saharan African populations. Frequencies of antigens commonly found in Amerindians, namely A2, A24(9), A28, A31(19), B35, B39(16), B40, B51(5), B62(15), Cw3, Cw4, Cw7, DR2, DR4, DR6, DR8, DR9, DQ3, and DQ4 (Petzl-Erler et al. 1993; Braun 1995), were not significantly increased in any of the samples in comparison to European and African averages.

Linkage Disequilibrium and Haplotype Frequencies. All 2-locus haplotypes occurring at frequency higher than 5% are shown in Tables 3 (for the white sample) and 4 (for the mulatto sample); those with a frequency between 5% and 1% are listed only if presenting significant linkage disequilibrium. Low-frequency haplotypes are not shown in the tables; thus, when mentioned below, their frequencies are given in the text.

In the white sample, typical European haplotypes (Imanishi et al. 1992a) predominate, as expected. However, a few characteristically African haplotypes (Imanishi et al. 1992a) are found at a very low frequency, such as A30(19)-B35 (0.06%), A30(19)-B42 (0.1%), B53-Cw4 (0.7%), and DR8-- DQ7(3) (0.5%). Haplotypes typically found at high frequencies in Guarani and Kaingang Amerindians (Petzl-Erler et al. 1993) are present, mostly at low frequency: A28-B40 (0.4%), A31-B35 (0.5%), A31-B51 (0.2%), DR16(2)-- DQ7(3) (1.5%), and DR6-DQ3 (1.1%). The mulatto sample has haplotypes commonly found in African populations: A30(19)-B35 (2.8%), A30(19)-B42, B53-Cw4, B17-DRS (2.6%), B53-DR6 (2.3%), DR8-DQ7(3), as well as European haplotypes: A1-B57(17), A2-B44(12) (1.6%), A2-B51(5) (1.3%), A24(9)-B35 (2.8%), etc., besides haplotypes shared by at least some populations of both groups: A2-B35 (3.8%), B35-Cw4, B7-Cw7, B44-Cw4 (1.9%), B7-DR15, etc., and Amerindian haplotypes, as DR16(2)-DQ7(3). This pattern reveals the high degree of admixture of this population.