Immunohistochemical Evaluation of NKP46 Receptor Expression and the Number of NK Cells in the Endometrium of Patients with Endometriosis

Background: Endometriosis is a medical condition that can cause infertility in women. Women with endometriosis experience a decrease in NK cell cytotoxic activity against endometrial cells, ultimately contributing to the spread of these cells. Objective: To assess the frequency of NK cells and the expression of the NKP46 receptor in endometrial tissue from patients with endometriosis using immunohistochemistry. Methods: 30 endometrial tissue specimens were collected from three groups of cases with mild (n=11), moderate (n=10), and severe endometriosis (n=9), respectively. Additionally, 20 normal endometrial tissue specimens were collected as the control group. Immunohistochemical staining was carried out using specific human monoclonal antibodies against CD56 and NKP46 molecules. Results: Cases with severe endometriosis had a significantly higher number of CD56(+) uterine NK cells (26.19 +/- 2.50) compared to fertile women (15.02 +/- 0.622) and women with mild to moderate endometriosis (p<0.001). However, there was no significant difference between the mild to moderate patients compared with the healthy women (p>0.05). Endometrial NKp46 expression was lower in women with severe endometriosis (0.447 +/- 0.0829) compared to fertile women (0.987 +/- 0.115, p=0.03). The NKp46(+)/CD56(+) cell ratio was also lower in women with severe endometriosis (0.019 +/- 0.003) compared to fertile women (0.072 +/- 0.011, p=0.01). Conclusion: Women with severe endometriosis demonstrated an increased rate of infiltrated uterine NK cells and a significant decrease in NKP46 expression compared to fertile women. Therefore, NK cells and the NKp46 receptor may be involved in the development of endometriosis.