Changes in the T-helper 1 and 2 cell populations during pregnancy in tacrolimus-treated women with repeated implantation failure and recurrent pregnancy loss.

Tacrolimus has received considerable attention as a treatment approach for infertility associated with maternal-foetal immune abnormalities, such as repeated implantation failure (RIF) and recurrent pregnancy loss (RPL). This study examined the changes in T-helper (Th) 1 and 2 cell populations during pregnancy in peripheral blood of tacrolimus-treated RIF patients who delivered a liveborn infant from August 2012 to February 2020 at the National Centre for Child Health and Development. A total of 58 eligible study subjects were divided into two groups according to the presence of a history of RPL: (i) RIF-alone group ( = 31); and (ii) RIF-plus-RPL group ( = 27). In a flow cytometric analysis, the Th1/Th2 cell ratios were significantly higher before pregnancy than after pregnancy, and during the first trimester than the second trimester in the RIF-alone group ( = 0.0071 and  = 0.0087, respectively). However, no significant differences were present in the RIF-plus-RPL group. Although the Th1 immunity was suppressed under tacrolimus treatment in both groups, a delayed reduction in the Th1 cell percentage after initiation of treatment was observed in the RIF-plus-RPL group. In conclusion, the cellular immune alterations in tacrolimus-treated patients with RIF were different depending on the presence or absence of a history of RPL.