The effectiveness and safety of intrauterine infusion of autologous regulatory T cells (Tregs) in patients with recurrent pregnancy loss and low levels of endometrial FoxP3(+) cells: A retrospective cohort study

Problem: Regulatory T cells (Tregs) are a specialized type of T cells that help maintain immune tolerance and homeostasis. The potential of Tregs cell-based therapies in treating diseases has been demonstrated in several clinical trials, which have shown promising outcomes and high safety in autoimmune diseases, transplant rejection, and graft-versus-host disease. However, their effectiveness and safety in improving endometrial receptivity and reducing pregnancy loss in human reproduction are unknown. Method of study: The study used a retrospective design and included patients with recurrent pregnancy loss (RPL) and lower levels of endometrial FoxP3(+) Tregs. Patients in the Tregs group (n = 33) received intrauterine Tregs infusion three times during the follicular phase, while the control group (n = 28) did not receive any intrauterine infusion. Results: The intrauterine infusion of autologous Tregs increased the levels of FoxP3(+) Tregs and CD56(+) NK cells. Patients in the Treg group had higher live birth rates and lower miscarriage rates, especially early miscarriage rates. However, the two groups had no differences in the implantation rate, clinical pregnancy rate, and percentage of preterm delivery. Conclusions: The findings suggest that intrauterine Tregs infusion may be a potential therapeutic approach for RPL. Further research in larger clinical trials is needed to confirm these findings.