HLA alleles association and recurrent spontaneous abortion in a São Luis/Maranhão population, in Brazilian Northeastern region

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To investigate the association of the HLA-A, -B and -DRB1 alleles with the occurrence of Recurrent Spontaneous Abortion. A case-control study of 200 women aged 18 to 35 years, consisting of a convenience sample of 100 women who had idiopathic recurrent spontaneous abortion and 100 women without abortion and with two or more children. Peripheral blood genomic DNA was extracted from 500l of Buffy Coat stored at -20°C. HLA typing was performed by the PCR-SSOP method (Polymerase Chain Reaction - Specific Sequence of Oligonucleotides Probes, One Lambda(r), CA, USA). The regions of the amplified DNA were exon 2 and 3 for the A and B loci and only exon 3 for the DRB1 locus. The HLA FUSIONTM program (One Lambda, Canoga Park, CA, USA, version 3.0) was used for HLA-A, HLA-B and HLA-DRB1 genotyping. Absolute frequencies and percentages and calculation of mean and standard deviation were used for standard statistical analysis. The qualitative variables were compared by the χ2 test with Yates correction or by Fisher's exact test. The odds ratio with the 95%CI was used for the comparisons, with the level of significance set at p<0.05. The frequency of the A*34 allele was significantly higher in the case group compared to control (4.0 versus 0.5%; p<0.05). Alleles A*24 (6.0 versus 12.5%; p<0.05) and B*35 (8.0 versus 20.5%; p<0.05) were significantly less frequent in the case group. Among the class II alleles, DRB1*03 showed a slightly higher frequency in the case group (11.0 versus 5.5%, p = 0.056). It was shown that the HLA-A*34 allele is a risk factor for recurrent spontaneous abortion, while the HLA-A*24 and HLA-B*35 alleles are associated with protection, and no allele of the DRB1 locus was associated with RSA.