Immunology / Inflammation

Immunology / Inflammation

Reproductive immunology is a field that explores the complex mechanisms by which the immune system maintains a delicate balance between defending against infections and tolerating reproduction-associated antigens. This discipline focuses in particular on the immune system’s ability to recognize pathogens while avoiding harmful responses against key reproductive structures such as sperm or the embryo.

In males, sperm are protected from the immune system by the blood–testis barrier. However, if this barrier is compromised—following, for example, an infection or trauma—sperm may come into contact with the immune system, potentially triggering the production of anti-sperm antibodies and leading to male infertility. Sylvie Breton’s team has discovered that certain cells in the epididymis, called clear cells, play a dual role: they support sperm maturation and contribute to immune defense. These cells produce chemokines that attract macrophages, helping to protect against infections while preserving tolerance to sperm.

In females, the lower genital tract is a critical interface between the body and the external environment, where immune protection against pathogens must coexist with tolerance to foreign reproductive antigens. An optimal vaginal microbial community, generally dominated by lactobacilli, plays a central role in this balance. Karine Dufresne’s team investigates how microbes influence reproductive health or disease in women. Recent studies show that a well-balanced vaginal microbiome is linked to improved fertility, full-term pregnancy, and protection against infections. Nevertheless, the role of the vaginal and uterine microbiota remains underrecognized. A deeper understanding of this microbial world may, in the long term, lead to preventive or therapeutic strategies to support reproductive health.

Understanding immune defense and inflammation is especially important in the context of infections that can threaten reproduction. Congenital toxoplasmosis, caused by Toxoplasma gondii, illustrates the consequences of immune defense failure during a critical stage of fetal development. Maritza Jaramillo’s team studies the mechanisms by which toxoplasma infection disrupts placental function and affects fetal development.

The balance between pro-inflammatory and tolerogenic immune responses is also key to pregnancy success. Carlos Reyes-Moreno’s team investigates the role of inflammatory and gestational cytokines in inflammation and metabolism related to cancer and pregnancy complications.

Moreover, the influence of immune cells on ovarian function is increasingly documented, particularly in the regulation of the ovarian cycle, folliculogenesis, and luteinization. Kalidou Ndiaye’s lab explores how immune cells affect ovarian activity.

In animals, these immunological mechanisms are equally critical. For example, endometritis in cows—an inflammation of the endometrium often caused by postpartum infection—is a major cause of infertility. Guillaume St-Jean’s team aims to better understand uterine inflammatory diseases, focusing especially on the Hippo signaling pathway and its role in uterine function and endometritis in cows.