Decidual Natural Killer Cells (CD56+) population In the Placental Bed in Accidental Haemorrhage

Abstract

Uterine NK cells are the most abundant leukocytes in preimplantation endometrium and early pregnancy deciduas. Maternal uterine NK cells are adjacent to, and have the ability to interact directly with the fetal trophoblasts. NK cells in both the uterus and the peripheral circulation are characterized by the presence of CD56 antigen. However, unlike the peripheral NK cells, the uterine NK cells can be divided by immunohistochemistry and flow cytometry into 2 subpopulations, the CD56dimCD16+ and the CD56bright CD16-. It is believed that the CD56bright CD16- population is the abundant population in the normal deciduas. Accidental haemorrhage is defined as abnormal complete or partial separation of normally implanted placenta after 20 weeks of gestation and prior to birth (Lindqvist and Happach, 2006). Placental abruption seems to be multifactorial. Its etiology is not fully understood but impaired placentation, placental insufficiency, intrauterine hypoxia, and uteroplacental underperfusion are considered the key mechanisms causing abruption (Rasmussen et al., 1999). Abruption results from a rupture of maternal decidual artery causing dissection of blood at the decidual-placental interface, around placental margin, or behind the membranes. Acute vasospasm of small vessels may be one event immediately preceding placental separation. Thrombosis of the decidual vessels with associated decidual necrosis and venous hemorrhage also are often present (Kraus et al., 2004). This study aimed at studying the role of uterine NK cells in placental abruption. The study was held in Ain Shams university Maternity hospital. It included 54 participants between 20 – 35 years old divided into two groups: