Knowledge of natural killer cell function could help screen for miscarriage

Researchers at the University of Warwick and University Hospitals Coventry and Warwickshire (UHCW) NHS Trust have identified the function of natural killer cells in the womb, which could play a key role in screening for miscarriage in pregnancies.

It is estimated that one in six known pregnancies will end in miscarriage. Currently most miscarriages cannot be prevented as they are most commonly caused by an abnormality in the chromosomes of the foetus. However, researchers at the University of Warwick and UHCW NHS Trust have determined the function of uterine natural killer (uNK) cells in pregnancy, giving rise to the possibility of screening for miscarriage.

It is estimated that one in six known pregnancies will end in miscarriage

Natural killer cells play a vital role in the body’s defence system against illness and disease. There are two types of uNK cells one located in peripheral blood and the other inuterine mucosa. It has long been known that these cells are present in the lining the womb. However, the new study of clearance of decidual cells by uNK cells in cycling human endometrium has led to the discovery previously unknown functions.

uNK cells remodel the lining of the womb at the time of embryo implantation by removing infl ammatory stressed cells – otherwise known as senescent cells. However, problems can occur as these uNK cells can be both under and over activated leading to excessive infl ammation or insuffi cient clearance increasing the chance of miscarriage.

Natural killer cells play a vital role in the body’s defence system against illness and disease

If senescent cells are not removed, then the embryo will fail to attach but if too many cells are removed the tissue will physically collapse. Professor Jan Brosens, from the Division of Biomedical Sciences Warwick Medical School, uses the analogy of swiss cheese to explain this, saying that “without holes, the embryo has nowhere to go which will cause implantation failure; but if the holes are too large, the tissue will physically collapse and lead to miscarriage.”

Approximately 15% of women who experience recurrent miscarriage have abnormal natural killer cell activity preventing effective implantation. Understanding the function of natural killer cells provides the opportunity to recognise when these cells are defective. “We hope in the future this new informa-
tion will be used to screen women at risk of  reproductive failure,” adds Professor Brosens,
highlighting the impact this research can have.

Approximately 15% of women who experience recurrent miscarriage have abnormal natural killer cell activity

Although the exact methods for screening have not yet been determined, knowledge of natural killer cells provides a hopeful possibility of detecting the chance of miscarriage. New possible treatments that enable the control of uNK cell activity have now been suggested for women suff ering repeated miscarriages or recurrent IVF failure. The contribution made by researchers at the University of Warwick could therefore aid in improved screening and potential prevention of miscarriage.