This study aims to evaluate the distribution of different lymphocyte subsets and other immune biomarkers in peripheral blood in healthy Danish females of reproductive age and to make a research biobank for future research. This data will serve as a reference to an ongoing study as well as future studies investigating the impact of the immune system on diseases affecting females in reproductive age.

A blood sample will be collected from 37 healthy Danish females of reproductive age; part of material will be analysed immediately and part of it will be stored in a research biobank for future research. The samples are collected by clinicians at the Department of Gynaecology at Aalborg University Hospital (AaUH), and these samples are on the same day delivered to at the Department of Clinical Biochemistry (DCB) and Department of Clinical Immunology (DCI) at AaUH, that will perform the sample analyses. The DCI will store the biobank material.

The blood samples will be collected in EDTA-, citrate- and heparin-stabilised tubes. A white blood cell differential count, progesterone level measurement, and the leukocyte subset analysis will be performed by personnel at the DCB and DCI at AaUH.

Serum-progesterone level will be measured on the same day or the day before the blood samples for immunology testing and biobank is collected to ensure that the participant has ovulated and is in the luteal phase. Only blood samples with a serum progesterone level >20 nmol/l will be accepted for the study and included in the biobank. The result of the serum-progesterone measurement may come after the immunology analyses have started, but if the progesterone level is <20 nmol/l, further analyses will be cancelled, and the biobank material will be destroyed.

The white blood cell differential count (WBC) will be obtained from the Sysmex XN-1000 blood analyser. The analysis for NK-cells, B-cells, and T-cell subsets, including Treg, Th1, Th2 and Th17 in EDTA stabilised samples will be performed by the DCI on a flow cytometer using antibodies specific for surface markers that are exclusive for each leukocyte subset.

Blood for the research biobank comprises the remaining tubes. The serum and plasma in these three tubes will after immediate centrifugation be aliquoted and stored in tubes at -80 C in a locked freezer.

Inclusion Criteria:

• - Healthy women of fertile age (18-41 years) with a regular menstrual cycle (22-35 days) who are in the luteal phase of their menstrual cycle at the time collecting the blood sample (day 20 to 28 of cycle and serum progesterone > 20 nmol/l at the day of blood sample). The group should consist of an approximately 1:1 ratio of women with ≥1 previous liveborn child and women with no previous pregnancy.

Exclusion Criteria:

• < 18 years old or >41 years old
• History of ≥1 known pregnancy loss including both spontaneous and missed abortions. An induced abortion is accepted if it was performed more than 2 years before study participation.
• Pregnancy within last 6 months
• Treatment with drugs acting on the immune system or hormonal contraceptive drugs either acting systemically or locally (intrauterine device releasing progesterone).
• Known disease with influence on the immune system and/or endocrine system
• Previously received a blood transfusion

upon reasonable request

within 3 months

upon reasonable request

No treatment intervention, only a blood sample is collected