Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 14 2 2015 04 15 217 221 EN Saeid Abediankenari Immunogenetic Research Center, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran. Faramars Farzad Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran. Zahra Rahmani Department of Obstetrics, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran. Mohammad Bagher Hashemi-Soteh Immunogenetic Research Center, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran. 2015 10 16 Human leukocyte antigen-G which is an immune tolerance effecter molecule has an important role in the maintenance of fetus during pregnancy. Abortion is one of the complications of pregnancy period.  In this research, we have studied levels of HLA-G 5, HLA-G7 isoforms in the abortion-threatened pregnant women in comparison with controls. In a case-control study, 101 abortion-threatened women and 101 healthy pregnant women (healthy controls) with age range 21-32 years were studied. Gene expression of HLA-5 and HLA-7 isoforms was analyzed by real-time polymerase chain reaction after mRNA extraction and cDNA synthesis. The results indicated that HLA-G5 was significantly lower in abortion-threatened women in comparison with the control group whereas HLA-G7 was not significantly differentbetween the 2 groups. HLA-G is a vital molecule during pregnancy that can be a key factor in prevention of abortion. It is concluded that determination of HLA-G5 can be of value in pregnancy. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/392 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/392/445