*4.2. PF Sample Collection*

PF samples were collected on the same day at the mid-follicular phase (8–10 day) of the menstrual cycle. The mid-follicular menstrual cycle phase was additionally confirmed by the ultrasound examination.

PF was aspirated from the cul de sac at the beginning of the standard laparoscopic procedure under general anesthesia. Samples of the peritoneal fluid contaminated with blood were excluded from the study. PF samples were centrifuged at 400g at 4 ◦C for 10 min and the cell-free supernatants were collected, aliquoted, and stored frozen at −80 ◦C until used for further evaluations and experiments. The mean yield of PF obtained from the endometriosis patients and the control subjects was 6.2 (range 2–12.5) and 4.6 (range 0.5–13) mL, respectively.
