Variation during the menstrual cycle of immune cell populations in human endometrium

Area of Science:

• Reproductive immunology
• Gynecologic pathology
• Endometrial biology

Background:

• The human endometrium harbors diverse immune cells crucial for reproductive processes.
• Understanding immune cell dynamics throughout the menstrual cycle is key to deciphering reproductive health and potential pathologies.

Purpose of the Study:

• To investigate the cyclical variations of bone marrow-derived immune cell populations within the human endometrium.
• To characterize the temporal changes of specific immune cell subsets, including T cells, macrophages, and CD56-positive large granular lymphocytes (LGLs), during the normal menstrual cycle.

Main Methods:

• Morphometric analysis of endometrial tissue sections.
• Immunohistological staining to identify and quantify specific immune cell markers (T cells, macrophages, CD56).

Main Results:

• T cell and macrophage populations remained relatively consistent throughout the menstrual cycle.
• CD56-positive large granular lymphocytes (LGLs) showed significant cyclical variation, with low numbers from day 10 to 19.
• LGL numbers sharply increased in the late luteal phase and decreased post-menstruation.

Conclusions:

• The endometrium exhibits dynamic immune cell changes, particularly in LGL populations, correlating with the menstrual cycle phases.
• The surge of CD56-positive LGLs in the late luteal phase may indicate a role in preparing the endometrium for potential implantation or early pregnancy.
• These findings contribute to understanding the immunological environment of early pregnancy and potential factors influencing reproductive success.