The article discusses the role of the immune system during pregnancy, challenging the notion that pregnancy is associated with immune suppression. It highlights the complex interaction between the fetal and maternal immune systems, emphasizing that the maternal immune system is not suppressed but rather actively involved in supporting pregnancy. Key points include: 1. **Immune Cells at the Implantation Site**: The presence of immune cells such as macrophages, natural killer (NK) cells, and regulatory T cells (Treg) is crucial for placental development, implantation, and decidual formation. Depletion of these cells can lead to pregnancy termination. 2. **Trophoblast-Immune Interaction**: Trophoblast cells play a significant role in recruiting and educating immune cells, modulating their function to support pregnancy. This interaction involves three stages: attraction, education, and response. 3. **Cytokine Profile During Pregnancy**: Pregnancy is characterized by a dynamic cytokine profile, with distinct phases. The first trimester is proinflammatory, the second trimester is anti-inflammatory, and the third trimester is again proinflammatory. 4. **Inflammation and Implantation**: Early implantation is marked by a high level of proinflammatory cytokines, which are essential for tissue repair and implantation. The endometrium undergoes significant cellular and molecular changes to facilitate implantation. 5. **Tissue Repair and Implantation**: Local injury to the endometrium can enhance implantation rates, suggesting that an inflammatory response may be beneficial for successful pregnancy. 6. **Trophoblast-Lumen Epithelium Synapse**: The trophoblast must attach to the uterine epithelium, which is regulated by cytokines and chemokines produced by immune cells, facilitating the attachment process. The article concludes by proposing a new paradigm for understanding the fetal-maternal immune interaction, emphasizing the importance of this interaction in maintaining a healthy pregnancy.The article discusses the role of the immune system during pregnancy, challenging the notion that pregnancy is associated with immune suppression. It highlights the complex interaction between the fetal and maternal immune systems, emphasizing that the maternal immune system is not suppressed but rather actively involved in supporting pregnancy. Key points include: 1. **Immune Cells at the Implantation Site**: The presence of immune cells such as macrophages, natural killer (NK) cells, and regulatory T cells (Treg) is crucial for placental development, implantation, and decidual formation. Depletion of these cells can lead to pregnancy termination. 2. **Trophoblast-Immune Interaction**: Trophoblast cells play a significant role in recruiting and educating immune cells, modulating their function to support pregnancy. This interaction involves three stages: attraction, education, and response. 3. **Cytokine Profile During Pregnancy**: Pregnancy is characterized by a dynamic cytokine profile, with distinct phases. The first trimester is proinflammatory, the second trimester is anti-inflammatory, and the third trimester is again proinflammatory. 4. **Inflammation and Implantation**: Early implantation is marked by a high level of proinflammatory cytokines, which are essential for tissue repair and implantation. The endometrium undergoes significant cellular and molecular changes to facilitate implantation. 5. **Tissue Repair and Implantation**: Local injury to the endometrium can enhance implantation rates, suggesting that an inflammatory response may be beneficial for successful pregnancy. 6. **Trophoblast-Lumen Epithelium Synapse**: The trophoblast must attach to the uterine epithelium, which is regulated by cytokines and chemokines produced by immune cells, facilitating the attachment process. The article concludes by proposing a new paradigm for understanding the fetal-maternal immune interaction, emphasizing the importance of this interaction in maintaining a healthy pregnancy.