HLA and complement factors alleles sharing in Italian couples with recurrent spontaneous abortions

Recurrent Spontaneous Abortion (RSA) is postulated to be due to several factors including immunogenetic mechanisms. Many studies have been conducted on the effect of the MHC region in the reproductive phenomena suggesting an immunological or genetic involvement in RSA. We studied couples with 3 or more abortions among a larger group of couples in which female partners were anti-cardiolipin antibodies negative, resulting in a population of 43 couples typed for HLA-A, B, C, DR, DQ. In 16 of these 43 couples, complement factors C4A, C4B, and Bf were typed. The data shows a statistically significant increase of C4B*Q0 in RSA patients (N = 32) compared with the control population (N = 44) (pc = .00147) and also a statistically significant increase of C4B*Q0 sharing in aborting couples (43.75%) against the expected sharing rate in the control population (1.86%) (p < .001). Frequency increase of C4B*Q0 allele in aborting population leads to the hypothesis that an imbalance of complement factors expression and activity can have detrimental effects on implantation and embryo survival. Additionally, the significant sharing rate of C4B*Q0 in couples with RSA could indicate the existence of a gene in linked to this allele predisposing to RSA and acting in a recessive manner if present in double copies in the fetus.