Lymphocyte immunotherapy in recurrent miscarriage and recurrent implantation failure.

Lymphocyte immunotherapy (LIT) emerged in the early 1980s as a new therapeutic proposal for couples with a history of recurrent miscarriages (RM) of unknown causes. Initial studies evaluated different LIT protocols with encouraging results. However, in the early 2000s, the effectiveness of LIT was questioned after an investigation, which suggested a negative impact of LIT on reproductive outcomes. Despite the controversies over the efficacy and safety of LIT for the treatment of RM, LIT has been utilized Worldwide. Recent meta-analyses have observed the effectiveness and safety of LIT in treating couples with a history of RM. Some studies also evaluated the use of LIT in cases of recurrent implantation failure (RIF) in in vitro fertilization cycles without promising results. Recent studies have proposed the intrauterine infusion of peripheral blood mononuclear cells in the treatment of RIF. This review describes the historical aspects of LIT and discusses its protocols, mechanisms of action, side effects, complications, and current evidence of the effectiveness in cases of reproductive failure.