Shall We properly Re-examine the Status of Allogeneic Lymphocyte Therapy for Recurrent early Pregnancy Failure?

Lymphocyte immunotherapy in recurrent miscarriage and recurrent implantation failure

PROBLEM

Lymphocyte immunotherapy (LIT) emerged in the early 1980s as a new therapeutic proposal for couples with a history of recurrent miscarriages (RM). However, in the early 2000s, the effectiveness of LIT was questioned. Recently, meta-analyses have observed the effectiveness and safety of LIT in treating couples with RM. Some studies evaluated the use of LIT in recurrent implantation failure (RIF) in in vitro fertilization cycles.

METHODS

This systematic and narrative review evaluated the data available in the literature regarding the efficacy and safety of the use of LIT. Searches in PubMed/Medline, Embase, and Cochrane Library databases were conducted, using the following keywords: "recurrent miscarriage," "lymphocyte immunotherapy," and "recurrent implantation failure".

RESULTS

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. It also discusses the use of LIT during the COVID-19 pandemic and new immunological therapies.

CONCLUSION

In the vast majority of studies, the use of LIT for RM couples has shown an improvement in pregnancy outcomes. The most of the current studies that support the evidence are quasi-experimental, with few randomized, double-blind studies (Level of evidence III). However, the current evidence are not convincing for the use of LIT in RIF patients.

Fetal rejection: infertility and immunity

Defective reaction toward fetal alloantigens could result in both recurrent spontaneous abortions (RSAs) and recurrent early pregnancy failures (REPFs), the latter existing in couples with unexplained infertility and multiple failures of implantation after in vitro fertilization embryo transfer. Immunological mechanisms leading to RSA and REPF seem to be different, although both syndromes probably have a genetic background that has not been identified so far. Despite the fact that antiphospholipid syndrome is a well-established cause of repeated pregnancy loss, the role of different autoantibodies existing in RSA and REPF patients needs to be elucidated. Immunotherapy is believed to correct the detrimental immune reactions; however, its real effectiveness and safety for the treatment of distinct forms of pregnancy loss need to be reconsidered.

T cells in normal pregnancy and recurrent pregnancy loss

This review focuses on the possible role of T cells in successful pregnancy and in unexplained recurrent abortion. The functions exhibited by Th1 and Th2 cells have suggested, perhaps in a simplistic way, that Th1-type cytokines, which promote allograft rejection, may compromise pregnancy, whereas the Th2-type cytokines, by inhibiting Th1 responses, promote allograft tolerance and therefore may improve fetal survival. However, Th1 cytokines are not always detrimental for pregnancy development. Th1 cytokines, depending on their time of expression, stage of gestation and relative concentrations, could have a positive role in successful pregnancy. Other cytokines (LIF, M-CSF) produced by T cells seem to be important for the maintenance of pregnancy. Hormones present in the microenvironment of the decidual T cells could be responsible, at least in part, for the cytokine profile of the T cells. Indeed, progesterone is a potent inducer of Th2-type cytokines (e.g. IL-4 and IL-5), LIF and M-CSF production by T cells, whereas relaxin induces T cells to produce IFNgamma. Of course, the success of pregnancy depends on many mechanisms induced by different type of cells. Th2 cells could be one of these.

Diagnosis and Treatment of Recurrent Miscarriage Associated with Immunologic Disorders: Is Paternal Lymphocyte Immunization a Relic of the Past?

Miscarriage is the most common complication of human pregnancy. Although the causes of recurrent miscarriage (RM) are various, immunologic aberrations between mother and fetus might be one of the causes of miscarriage. Immune responses fall into two categories: autoimmune and alloimmune. Currently, no appropriate diagnostic method has been established to identify alloimmune causes. We observed that NK cell activity in women with RM was higher than that in women without a history of miscarriage. Functional or quantitative analysis of NK cells could be used to identify alloimmune causes. Paternal lymphocyte immunization has been the most widely used treatment for alloimmune-mediated miscarriages. However, the latest Cochrane review by Scott reached the current conclusion that lymphocyte immunization therapy provided no significant beneficial effect over placebo in preventing further miscarriage. Approximately 70% of Japanese university hospitals are still performing paternal lymphocyte immunization. Is paternal lymphocyte immunization a relic of the past? Randomized controlled trials based on adequate patient selection in Japan should provide an answer to this question.