Specialized immunological studies in the diagnostics of idiopathic infertility and recurrent miscarriages have limited applicability, as the role of the immune system in these conditions is not thoroughly understood. In ovulatory cycles, changes occur in the populations of uterine lymphocytes, which may influence the receptivity of the endometrium and the implantation of the embryo. Particularly notable are the changes in natural killer (NK) cells, which reach their peak during the luteal phase and regulate the invasion of the trophoblast. The dominant NK cells exhibit a CD56bright phenotype and differ in cytokine profiles from peripheral blood cells. Cyclical changes also affect macrophages and T lymphocytes; however, it is unclear whether their proportions differ in women with reduced fertility. There is a need to investigate how the composition of lymphocytes in blood influences the populations in the endometrium. The aim of this study is to analyze the correlation between peripheral and endometrial lymphocytes in women with idiopathic infertility and recurrent miscarriages, compared to fertile women.

A cross-sectional study will be conducted among women aged 18-45 years undergoing aspiration biopsy as part of the diagnosis of: i) idiopathic infertility, ii) recurrent miscarriages, iii) other conditions requiring histopathological examination of the endometrium (control).

A 2 ml endometrial biopsy will be collected using the NEXODIS suction cannula on day 20-22 of the cycle, after confirmation of a negative result of B-human chorionic gonadotropin in the blood, and divided into 2 parts: 1 ml will be secured and sent for cytometric examination. At the same time, a peripheral blood sample (10 ml) will be collected in accordance with the SU in-hospital procedure and sent for cytometric examination.

Labeled blood cells and isolated single endometrial cells will be analyzed by flow cytometry using the FACSCanto2 system (BD Biosciences, USA). Blood cells will be stained directly with a panel of antibodies, and endometrial samples will be crushed and filtered before staining to isolate single cells. Then, the stained cells will be washed, erythrocytes will be lysed and centrifuged. It is planned to use a panel of monoclonal antibodies conjugated with fluorochromes, recognising the following markers: CD45, CD56, CD16, CD3, CD64, CD206, CD163, CD80, CD86 and CD138. The study population will be characterised in terms of age, BMI, gynecological data (surgeries, course of the menstrual cycle, nature of bleeding, ultrasound data) and obstetric data (pregnancies, deliveries, miscarriages). Characteristics of the study population, results of cytometric, histopathological, immunohistochemical endometrial and blood cytometric tests and their mutual correlation will be analysed using standard statistical methods.

Inclusion Criteria:

• age 18-45 years
• idiopathic infertility
• at least 2 miscarriages
• other benign gynecological conditions subjected to endometrial sampling

Exclusion Criteria:

• miscarriage within last 3 months
• abdominal/uterine surgery within last 3 months
• viral/bacterial infection within last 3 months
• antibiotic therapy within last 3 months

Women undergoing endometrial aspiration biopsy for the diagnosis of: i) idiopathic infertility, ii) recurrent miscarriages, iii) other conditions requiring histopathological examination of the endometrium (control).