P-339 Activities and changes in the number of natural killer cells in endometriosis: systematic review and meta-analysis
Authors: Getnet Gedefaw A , Zhang T J , Kassie B A , Ling W L , Wang C C R 
Published: June 2023

Abstract

Study question
What are the differences in peripheral, uterine, and peritoneal NK (uNK, pNK, pfNK) cell counts/percentages, and activities in women with endometriosis compared controls

Summary answer
The mean percentage level of uNK, pNK, and peritoneal NK (pfNK) cells has no significant difference in women with endometriosis compared controls

What is known already
NK cells play an important role in the pathogenesis of endometriosis

Study design, size, duration
This systematic review and meta-analysis included 36 experimental studies (case control and cross sectional). Narrative review is also conducted on the NK cell activity, cytokine expression, regulations and receptors.

Participants/materials, setting, methods
Women suffering with endometriosis confirmed with laparoscopy and/or pathology was the cases whereas, women having different pelvic pathology such as myoma, ovarian cyst, healthy woman and verified not having endometriosis with laparoscopy and/or pathology was considered as controls for this study.
Databases (PubMed, Web of Science, Scopus, Google scholar, and EMBASE through OVID) were used to search for the available studies. RevMan 5.4 and STATA 14 were used to analyze the data.

Main results and the role of chance
The mean percentage level of uNK, pNK, and peritoneal NK (pfNK) cells has no significant difference (standard mean difference SMD 0.13, 95%CI -0.35, 0.62; P = 0.59, I2 74%; total 393 women, 6 studies), (SMD 0.27, 95%CI -0.07, 0.61; P = 0.12, I2 80%; total 825 women, 11 studies), and (SMD 0.31, 95%CI -0.68, 01.29; P = 0.59, I2 94%; total 404 women,7 studies) in endometriosis patients compared with controls respectively. The pooled NK (uNK, pNK, pfNK) cell cytotoxicity/activity level is significantly higher in controls compared with women with endometriosis (MD 5.43, 95%CI 2.29, 8.57; P &lt; 0.007, I2 50%; total 323 women, 7 studies). The NK cytotoxicity/activity level in early stages of endometriosis has no significant difference compared with advanced stages of endometriosis (MD 2.29, 95%CI –1.98-6.57; P = 0.29, I2 87%; total 263 women, 7 studies). There are variations in studies conducted in NK cell activities in endometriosis: broadly categorized as NK cell cytotoxicity, cytokine expression and NK cell regulation and receptors (Inhibition and activation). The cytotoxic activity of NK cells decreased in women with endometriosis and correlated with the severity of the disease, however the cytokine expression and inhibitor receptors are equivocal across studies.

Limitations, reasons for caution
We unable to conduct sub-group analysis to investigate the cytotoxic activity of NK cell in women with endometriosis and its stages in different samples such as pNK, uNK, and pfNK due to the lack of studies for the analysis.

Wider implications of the findings
This study revealed that the activity of NK cells in women with endometriosis is significantly lower than controls.Though the mean difference of NK cell count and percentage has no significant difference, the cytotoxicity activity of NK cell is higher in controls compared with women with endometriosis

Trial registration number
CRD42022384060