Table 1.

PICO framework for study selection.

Population	Include: Women between menarche and menopause with all stages of surgically confirmed endometriosis and animal models with menstrual cycle. Exclude: Women with adenomyosis or other gynaecological diseases, idiopathic infertility, immune diseases, undergoing immune or hormonal therapy. Women with no menstrual cycles, and animal models with oestrous cycle.
Intervention	Include: In vitro and in vivo studies of CD8+ T cells in endometriosis related tissues, such as but not limited to peripheral blood, peritoneal fluid, eutopic endometrium and ectopic lesions of patients and animal models with endometriosis. Exclude: Meta-analyses of papers (but not datasets), systematic reviews and other reviews, case reports or case series, and organizational guidelines.
Control	Include: Healthy women and animal models without endometriosis. Exclude: Studies with no controls, poorly defined controls, or poor controls e. g. women with adenomyosis, acute pelvic inflammatory disease, idiopathic infertility, hydro/pyo/hematosalpinx, immune diseases, undergoing immune or hormonal therapy. Women with no menstrual cycle, and animal models with oestrous cycle.
Outcome	Include: Differences in measurable parameters (e. g. concentration, activation status, cytokine production) related to CD8+ T cells in patients and animal models with endometriosis when compared to healthy controls. Association between CD8+ T cells and disease stage, treatment response, recurrence rate after surgery, pregnancy rate, live birth rate, miscarriage rate. Exclude: Studies with no CD8+ T cell outcomes.