Mammalian peripheral blood mononuclear cells, such as T and B lymphocytes, and monocytes, have a positive effect on the endometrium and its receptors through cytokine secretion. Furthermore, peripheral blood mononuclear cells help in placental formation and regulate immune tolerance during placental development.

Various research groups have reported that intrauterine administration of peripheral blood mononuclear cells, either alone, in a medium supplemented with human chorionic gonadotropin (HCG), or with corpora lutea, significantly increased pregnancy, implantation, and live birth rates. Furthermore, studies have shown that fetal rejection can be prevented

by transferring B lymphocytes isolated from the uterus of normal pregnant mice into animals prone to miscarriage. B lymphocytes produce IgG-like antibodies with high affinity for antigens but are unable to stimulate host defense mechanisms, thereby protecting the fetus from maternally derived antibodies at the fetal-maternal interface.

In addition to peripheral blood cells, platelets also participate in human embryo implantation and play an essential role in fetal-maternal communication and endometrial remodeling. Furthermore, platelets actively participate in corpus luteum formation by regulating neovascularization and luteinization.

 Platelets may also help increase birth rates. This claim is well supported by the high pregnancy rates achieved after intrauterine platelet infusion prior to mating. Similar results have been observed in patients diagnosed with RIP treated with intrauterine platelet administration. Recently, subcutaneous treatment has been used to reduce miscarriage rates and improve reproductive outcomes. In mice, mesenchymal stem cell transplantation improved reproductive performance by enhancing the expression of interleukin 10 (IL-10) and TGF-β, as well as decreasing the expression of tumor necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ) mRNA.