Introduction
Reproductive immunology explains how the maternal immune system accepts a genetically different fetus, how the placenta and decidua form an immune interface, and how immune mechanisms can cause infertility, implantation failure and pregnancy loss. For the exam, know the key terms, the cells and antigens involved, and the main clinical syndromes with their prevention and treatment.
The immunological paradox of pregnancy
About half of the fetal genome is inherited from the father, so the fetus is a semi-allograft that expresses paternal antigens the mother has never encountered. Yet it is normally not rejected. Pregnancy is therefore a controlled, local state of immune modulation rather than general immunosuppression: the mother keeps her defence against infections while tolerance operates at the maternal-fetal interface.
- Pregnancy depends on immune tolerance restricted to the feto-maternal interface.
- Features: no rejection despite paternal alloantigens, a locally shifted (Th2-type and regulatory) cytokine profile, and preserved resistance to pathogens.
- Failure in either direction causes disease: insufficient tolerance leads to alloimmune injury and loss, while misdirected or excessive immunity contributes to infertility, placental insufficiency and autoimmune complications.