Abstract:

Recurrent spontaneous abortion (RSA) refers to the occurrence of two or more consecutive pregnancy losses before 28 weeks of gestation with the same partner. The RSA pathogenesis is complex, including the immune factor. Previous studies have showed that natural killer (NK) cells are closely related to RSA. There are two hypotheses regarding the origin of NK cells. They may originate from hematopoietic progenitor cells (HPCs) in the endometrium, or produce by the tissue-resident NK (trNK) cells. According to the phenotype and function, NK cells can be divided into multiple subsets and subtypes, each with different functions. During pregnancy, NK cells play important roles, such as regulating trophoblast invasion, participating in materno-fetal immunity, and promoting fetal growth. However, the abnormal functions of NK cells may lead to pregnancy failure. In RSA patients, the overactivity and dysfunction of decidual NK cells, the disordered polarization process and the changed number and cytotoxicity of uterine NK cells, could be closely related to the occurrence of RSA. This article is focused on the origin, classification and functions of NK cells, as well as the relationship with RSA, in order to provide a theoretical basis for understanding the pathogenesis of RSA and clinical diagnosis and treatment.

Key words: Killer cells, natural, Abortion, habitual, Pregnancy, Immunity, Immune tolerance