HLA-class I antigens in patients with unexplained recurrent abortion

In order to clarify the genetic background of recurrent spontaneous abortio n, the frequency of HLA-A, -B, and -C alleles was analyzed in eighty-nine p atients with a history of unexplained primary recurrent abortion. The frequ ency of each BLA-A, -B, and -C antigen allele was calculated in patients wi th recurrent abortion and their husbands, and compared with the frequencies in the general population represented by 207 individuals in the Niigata di strict of Japan. The incidence of individuals homozygous for the HLA-A, -B, and -C alleles was also compared between the patient group and the control group. The frequency of HLA-335 in the patient group (5 of 89, 5.6 %) was significantly lower than in the general population (40 of 207, 19.3 %) (Odd s Ratio, 0.25; 95 % Confidence Interval, 0.09-0.65; P < 0.005; Pc, not sign ificant). The frequencies of other HLA-A, -B, and -C alleles were not signi ficantly different between the patient group and the general population. No significant difference in the frequency of HLA-A, -B, and -C alleles was o bserved between the husband group and the general population. The incidence of individuals homozygous for HLA-A, B, or -C alleles in the patient group was not significantly different from the general population. The significa ntly lower frequency of HLA-B35 in patients with unexplained recurrent abor tion suggests that the Th2-associated immune reactions may be lacking in su ch patients, as it has been reported that an enhanced Th2 response in conju nction with a decreased T Th1 response is a common immune reaction in HLA-B 35-positive individuals.