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Pregnancy problems including recurrent pregnancy loss, repeated implantation failure and pre‐eclampsia are common problems in the reproductive ages. Different reasons such as genetic, immunological, and environmental agents and also infections could develop these complications. In those cases in which the cause of the abortion is diagnosed, the chance of a successful pregnancy is increased by eliminating defective factors. However, in patients with unknown causes, there may be an imbalance in immune cells pattern. As a matter of fact, an inappropriate immune response is often associated with a failed pregnancy. Hence, the focus of treatment is to increase tolerance, not to suppress maternal immune system. These findings are linked to an elevated number of Treg cells and immune checkpoints through normal pregnancy. The present review discusses the balance of myeloid‐derived suppressor cells, natural killer cells, T cells, and immune checkpoints, and also targeting them to maintain pregnancy and prevent associated complications. [ABSTRACT FROM AUTHOR]

Objectives: This investigation aims to evaluate the association between the concentration of cell-free DNA (cfDNA) in the spent culture medium (SCM) with implantation rate and the maternal immune system in the invitro fertilization (IVF). In this study, 30 embryos were cultured and scored according to Gardner's criteria. SCM was gathered on day five from every embryo to analyze the quantity of cfDNA. The real-time PCR technique evaluated the expression level of transcription factors, including Foxp3, RORγt, GATA3, and T-bet. The percentage of Th1, Th2, Th17, Treg, NK cells, and NK cells cytotoxicity was evaluated by flow cytometry. Results: The concentration of cfDNA in the β-HCG (-), β-HCG (+), and ongoing pregnancy groups were 20.70 ± 9.224 ng/µL, 27.97 ± 7.990 ng/µL, and 28.91 ± 8.566 ng/µL, respectively. The ratio of Th1/Th2 and Th17/Treg reduced significantly in pregnant women, as well as the level of NK cells and NK cytotoxicity cells fell dramatically in the ongoing pregnancy group. The expression level of RORγt and T-bet declined while the expression level of Foxp3 and GATA3 increased considerably in pregnant mothers. Our investigation revealed that the concentration level of cfDNA in SCM could not be associated with implantation rate, prediction of ongoing pregnancy, and maternal immune system. [ABSTRACT FROM AUTHOR]

Background: The COVID-19 pandemic has become the world's main life-threatening challenge in the third decade of the twenty-first century. Numerous studies have been conducted on SARS-CoV2 virus structure and pathogenesis to find reliable treatments and vaccines. The present study aimed to evaluate the immune-phenotype and IFN-I signaling pathways of COVID-19 patients with mild and severe conditions. Material and methods: A total of 100 COVID-19 patients (50 with mild and 50 with severe conditions) were enrolled in this study. The frequency of CD4 + T, CD8 + T, Th17, Treg, and B lymphocytes beside NK cells was evaluated using flow cytometry. IFN-I downstream signaling molecules, including JAK-1, TYK-2, STAT-1, and STAT-2, and Interferon regulatory factors (IRF) 3 and 7 expressions at RNA and protein status were investigated using real-time PCR and western blotting techniques, respectively. Immune levels of cytokines (e.g., IL-1β, IL-6, IL-17, TNF-α, IL-2R, IL-10, IFN-α, and IFN-β) and the existence of anti-IFN-α autoantibodies were evaluated via enzyme-linked immunosorbent assay (ELISA). Results: Immune-phenotyping results showed a significant decrease in the absolute count of NK cells, CD4 + T, CD8 + T, and B lymphocytes in COVID-19 patients. The frequency of Th17 and Treg cells showed a remarkable increase and decrease, respectively. All signaling molecules of the IFN-I downstream pathway and IRFs (i.e., JAK-1, TYK-2, STAT-1, STAT-2, IRF-3, and IRF-7) showed very reduced expression levels in COVID-19 patients with the severe condition compared to healthy individuals at both RNA and protein levels. Of 50 patients with severe conditions, 14 had anti-IFN-α autoantibodies in sera. Meanwhile, this result was 2 and 0 for patients with mild symptoms and healthy controls, respectively. Conclusion: Our results indicate a positive association of the existence of anti-IFN-α autoantibodies and immune cells dysregulation with the severity of illness in COVID-19 patients. However, comprehensive studies are necessary to find out more about this context. 5mo_nwLJpK7s-uZity9h4- Video abstract [ABSTRACT FROM AUTHOR]

Numerous treatment strategies have so far been proposed for treating refractory thin endometrium either without or with the Asherman syndrome. Inconsistency in the improvement of endometrial thickness is a common limitation of such therapies including tamoxifen citrate as an ovulation induction agent, acupuncture, long-term pentoxifylline and tocopherol or tocopherol only, low-dose human chorionic gonadotropin during endometrial preparation, aspirin, luteal gonadotropin-releasing hormone agonist supplementation, and extended estrogen therapy. Recently, cell therapy has been proposed as an ideal alternative for endometrium regeneration, including the employment of stem cells, platelet-rich plasma, and growth factors as therapeutic agents. The mechanisms of action of cell therapy include the cytokine induction, growth factor production, natural killer cell activity reduction, Th17 and Th1 decrease, and Treg cell and Th2 increase. Since cell therapy is personalized, dynamic, interactive, and specific and could be an effective strategy. Despite its promising nature, further research is required for improving the procedure and the safety of this strategy. These methods and their results are discussed in this article. [ABSTRACT FROM AUTHOR]

One of the most common diseases in the present era is cancer. The common treatment methods used to control cancer include surgery, chemotherapy, and radiotherapy. Despite progress in the treatment of cancers, there still is no definite therapeutic approach. Among the currently proposed strategies, immunotherapy is a new approach that can provide better outcomes compared with existing therapies. Employing natural killer (NK) cells is one of the means of immunotherapy. As innate lymphocytes, NK cells are capable of rapidly responding to cancer cells without being sensitized or restricted to the cognate antigen in advance, as compared to T cells that are tumor antigen‐specific. Latest insights into the biology of NK cells have clarified the underlying molecular mechanisms of NK cell maturation and differentiation, as well as controlling their effector functions through the investigation of the ligands and receptors engaged in recognizing cancer cells by NK cells. Elucidating the fact that NK cells recognize cancer cells could similarly show the mechanism through which cancer cells possibly avoid NK cell‐dependent immune surveillance. Additionally, the expectations for novel immunotherapies by targeting NK cells have increased through the latest clinical outcomes of T–cell‐targeted cancer immunotherapy. For this emerging method, researchers are still attempting to develop protocols for conferring the best proliferation and expansion medium, activation pathways, utilization dosage, transferring methods, as well as reducing possible side effects in cancer therapy. This study reviews the NK cells, their proliferation and expansion methods, and their recent applications in cancer immunotherapy. [ABSTRACT FROM AUTHOR]

The mammalian target of rapamycin (mTOR) is a member of the evolutionary phosphatidylinositol kinase‐related kinases (PIKKs). mTOR plays a pivotal role in the regulation of diverse aspects of cellular physiology such as body metabolism, cell growth, protein synthesis, cell size, autophagy, and cell differentiation. Immunologically, mTOR has a fundamental part in controlling and shaping diverse functions of innate and adaptive immune cells, in particular, T‐cell subsets differentiation, survival, and metabolic reprogramming to ultimately regulate the fate of diverse immune cell types. Researchers report that rapamycin, a selective mTOR inhibitor, and immunosuppressive agent, has surprising immunostimulatory effects on inducing both quantitative and qualitative aspects of virus‐specific memory CD8+ T‐cells differentiation and homeostasis in a T‐cell‐intrinsic manner. The mTOR signaling pathway also plays a critical role in dictating the outcome of regulatory T cells (Treg), T helper 17 (Th17) cells, and natural killer (NK) cells proliferation and maturation, as well as the effector functions and cytotoxic properties of NK cells. Manipulation of mTOR activity is a critical therapeutic approach for pharmacological agents that seek to inhibit mTOR. This approach should enhance specific memory CD8 + T‐cells responses and induce fully functional effector properties of NK cells to provoke their antitumor and antiviral activities. [ABSTRACT FROM AUTHOR]

Background: Recurrent miscarriage (RM) has a multifactorial etiology mainly due to chromosomal abnormalities and immunological factors. Treating RM has remained to be a challenging issue and the role of intravenous immunoglobulin (IVIG) in treating RM is still controversial. Materials and Methods: This study aimed to evaluate the changes in natural killer (NK) cells' frequency and cytotoxicity in patients with RM who received the IVIG therapy. A total of 78 women with a history of three or more recurrent miscarriages were included and their peripheral blood was drawn in case of positive pregnancy test. On the same date, 400 mg/kg of IVIG was administrated intravenously in 38 women and it continued every four weeks through weeks 30–32 of gestation. The remaining 40 patients with RM were included to be the untreated control group. Then, the effects of IVIG on NK cell frequency, cytotoxic activity, and the expression of inhibitory and activating receptors in the patients with RM, pre and posttreatment were assessed. Results: NK cells percentage and cytotoxicity were significantly reduced in the IVIG‐treated patients after 32 weeks of gestation (p < 0.0001). Expression levels of inhibitory receptors was increased, however, the expression levels of activating receptors were significantly decreased after the IVIG therapy. Pregnancy outcome after the treatment was significantly higher (86.8%) in the IVIG‐treated patients than controls (45%; p = 0.0006). Conclusion: Our results suggested that women with RM may benefit from IVIG as a therapeutic approach and the frequency and functional status of peripheral NK cells may serve as a valuable predictive factor of therapy response. [ABSTRACT FROM AUTHOR]

Natural killer (NK) cells are key players of the innate immune system. NK cells provide protection against infectious pathogens and malignancies in cell. This characteristic may be attributable to their intrinsic diverse potentialities and also their cooperation with adaptive immune lymphocytes, known as B and T cells. The growth, recurrence, and metastasis of cancer cells, and the failure of cytoreductive therapies against cancer cells are due to the small population of intratumor stem‐like cells, called cancer stem cells (CSCs). Furthermore, NK cells can efficiently eradicate heterogeneous tumor cells after a long‐term treatment. Therefore, NK cell–based therapy is a promising strategy to target and break CSC‐associated resistance to anticancer drugs treatment. In this review, we have presented an overview of the emerging knowledge of the characteristics, diversities, and mechanism‐driven immune surveillance of human NK cells and advances in NK cell–based immunotherapies. Finally, we will discuss how these cells can be applied to introduce the next generation of vaccine‐ and immune‐based approaches to prevent drug resistance. [ABSTRACT FROM AUTHOR]

RIF (repeated implantation failure) women with immunologic basis and cellular abnormalities may benefit from intravenous immunoglobulins (IVIG) as an immunomodulator based on different studies. In this study, we evaluated the effect of IVIG on the frequency and function of Th17 and Treg cells, as two important subgroups of CD4+T cells in implantation and pregnancy rates. Seventy-two RIF patients with preconception Th1⁄Th2 ratio and natural killer (NK) cells frequency and activity elevation were selected and divided into two groups; 40 out of 72 received IVIG, aspirin, and heparin (anoxaparin) and constituted the treatment group and 32 patients received aspirin and heparin (anoxaparin) and no IVIG and were the control group. Th17, Treg frequency, transcription factors, cytokine gene expression, and cytokine secretion were evaluated by flow cytometry, real-time PCR, and ELISA, respectively. Post-treatment evaluation of the IVIG grouprevealed a significant increase in Treg associated parameters such as Treg frequency (p= 0.0186), Foxp3 (p= 0.0004), and cytokine mRNA levels (IL-10, p = 0.0058 and TGF- β,p= 0.0038), however, in the case of Th17, a significant difference was only observed in a reduction in the RORγt mRNA level (p= 0.0218). In conclusion, IVIG therapy may be a good choice in the treatment of implantation failure in RIF women especially with an immunologic basis, and may improve the implantation and pregnancy rate by affecting immunoregulatory mechanisms such as Tregs. Abbreviations: RIF: repeated implantation failure; IVIG: intravenous immunoglobulin; Th17: T helper 17; Treg: T regulatory; NK cells: natural killer cells; PCR: polymerase chain reaction; ELISA: enzyme-linked immunosorbent assay;RORγt: RAR-related orphan receptor gamma;Foxp3: forkhead box protein P3; IL-17: interleukin-17; LMWH: low-molecular weight heparin; dNK: decidual NK cells [ABSTRACT FROM AUTHOR]

Oryzatensin (ORZ) can reduce potentially IFN-γ secretion by natural killer (NK) cells. Therefore, current study was designed to evaluate the effects of ORZ treatment on peripheral blood mono-nuclear cells (PBMCs) cytokine secretion, proliferation and also to evaluate vascular endothelial growth factor (VEGF) and Matrix Metalloproteinase 9 (MMP-9) expression in HEP-G2 cell line after culture with ORZ-stimulated PBMCs. In this ex-vivo study, PBMCs from apparently healthy male volunteers (n=25) aged 20-30 were isolated by ficoll density gradient. Tetrazolium colorimetric test (MTT assay), ELISA test and real time PCR were performed to evaluate PBMCs proliferation, PBMCs cytokine secretion and the genes expression accordingly. The results of MTT assay showed that ORZ significantly stimulated proliferation of the isolated PBMCs. The results also indicated that ORZ treatment significantly decrease and increase IFN-γ and IL-4 secretion by isolated PBMCs, respectively. Also, VEGF and MMP-9 expression significantly increased in HEP-G2 cells after culture with ORZstimulated PBMCs. The previous studies have introduced ORZ-like peptide for pharmacological purpose and in this study we get to the conclusion that the administration of this peptide may change the immune system response and sensitize target populations to cancer. [ABSTRACT FROM AUTHOR]

Background: Natural killer (NK) cells play an important role in early stages of innate immune responses against viral and tumoral attacks. Activation of NK cells by leishmaniasis results in secretion of cytokines such as interferon (IFN)-γ and tumor necrosis factor (TNF)-α, which enhances the phagocytosis and clearance of parasite. Lipophosphoglycan 3 (LPG3), the Leishmania homologous with GRP94 (glucose regulated protein 94), a member of HSP90 family, contributes to LPG assembly as the most abundant macromolecule on the surface of Leishmania promastigotes. Methods: We purified NK cells from healthy individuals (n=10) using magneticactivated cell sorting (MACS) technology. Purified NK cells were co-incubated with different concentrations of recombinant LPG3 (rLPG3), and its N-terminal (NT) and C-terminal (CT) fragments. Finally, the production of IFN-γ and TNF- α by NK cells were measured by ELISA. Results: Recombinant LPG3 but not its fragments (CT and NT), can significantly enhance the production of TNF-α by NK cells (P<0.05). Moreover, rLPG3, CT, and NT fragments were markedly stimulated the secretion of IFN-γ by NK cells (P<0.001). Conclusion: The Leishmania LPG3 antigen can effectively activate NK cells, in vitro. Leishmania LPG3 participates in the innate immunity against leishmaniasis and thereby improves the effective parasite destruction. However, its efficiency should be tested in vivo. [ABSTRACT FROM AUTHOR]

• Recurrent pregnancy loss, also known as RPL, happens to 2–5% of women of reproductive age. • Immune system between the mother and the fetus plays an important role in the acceptance of the fetus and maintaining the pregnancy. • Modulation of the immune system by lymphocyte immunotherapy (LIT) is a reasonable way to prevent embryo rejection. • Pro-Inflammatory cytokines decline following subcutaneous LIT of women with RPL. In order to prevent miscarriage in RPL patients, the goal of this study was to determine how well lymphocyte immunotherapy (LIT) works in modifying immunological responses produced by cells, cytokines, transcription factors, and microRNAs. 200 RPL patients and 200 healthy controls were included in the study. Using flow cytometry, it was possible to compare the frequency of cells before and after lymphocyte treatment. Real-time PCR was used to assess the gene expression levels of transcription factors, cytokines, and microRNAs. ELISA method was used to evaluate the level of secretion of cytokines in the serum. Primary evaluation of the immune profile between healthy controls and RPL cases showed a higher frequency of Th17, NK, B cells and a lower frequency of Treg cells in RPL cases. Also, pro-inflammatory cytokines showed increased expression at mRNA and protein levels in the RPL group in comparison with the control group. Whereas, anti-inflammatory cytokines showed decreased expression in RPL patients. Decreased and increased frequency of Th17 and Treg lymphocytes observed in RPL cases following LIT, respectively. The same results obtained for RORγt and FoxP3 mRNA expression as transcription factor of Th17 and Treg cells, respectively. NK cell cytotoxicity decreased after LIT in RPL patients. miR-326a and miR-155 expression after LIT reduced, but miR-146a and miR-10a expression increased in RPL instances. LIT in RPL cases causes to elevation and modulation of anti-inflammatory and pro-inflammatory cytokines. Our data showed that lymphocyte therapy can be proposed as an effective therapeutic agent in RPL patients with immunological background by a modulating inflammatory condition. [ABSTRACT FROM AUTHOR]

Preeclampsia (PE), as a pregnancy-specific syndrome, has become one of the main causes of maternal and fetal mortality worldwide and is known as a major risk factor for preterm birth. PE is typically characterized by hypertension, significant proteinuria, and an excessive maternal systemic inflammatory response. Recent evidences provide support for the notion that Natural killer T (NKT) cells (a small, but significant immunoregulatory T cell subset of human peripheral blood lymphocytes) play pivotal roles in pregnancy. NKT cells with unique transcriptional and cytokine profiles exist in different peripheral tissues acting as mediators between the innate and adaptive immune systems. NKT cells secrete Interleukin-4 (IL-4) and Interferon-γ (IFN-γ) which might regulate the balance between Type 1 T helper (Th1) and Type 2 T helper (Th2) responses. During pregnancy, maternal immunity is biased towards type II cytokine production to inhibit the function of type I cytokines that could be harmful for the developing fetus. This shift to type II cytokines does not occur in preeclamptic patients. In this review, we discuss the numbers, phenotype, changes, and the functional activity of Natural killer T (NKT) cells during normal pregnancy and preeclampsia. [ABSTRACT FROM AUTHOR]

Background Women with elevated natural killer (NK) cell frequency and function during pregnancy, suffer from recurrent pregnancy loss (RPL). In the present study, the possible effect of intravenous immunoglobulin (IVIG) administration on Th1 and Th2 cell frequency, cytokine secretion, and expression of transcription factors is compared between RPL patients and control group. Materials and methods Totally, 44 women with a history of RPL (32 women as treated group and 12 as control group) were enrolled in the study. The frequency of Th1 and Th2 lymphocytes, the expression of transcription factors related to these cells and the serum levels of associated cytokines were assessed by flowcytometry, real-time PCR and ELISA, respectively. All, assessments were performed both before and after treatment with IVIG. Results A significant reduction in Th1 lymphocyte frequency, transcription factor expression and cytokine levels were observed in IVIG-treated group, while all the above parameters indicated a significant increase for Th2 lymphocytes. Th1/Th2 ratio decreased significantly (p value < 0.0001) at the end of treatment and 28 out of 32 (87.5%) women in IVIG-treated group had live birth in comparison with 5 out of 12 (41.6%) in untreated group. Conclusion IVIG administration proves to be an efficient therapeutic strategy which is able to enhance the success rate of pregnancy through a shift in Th2 responses. Furthermore, IVIG presents efficacy for the treatment of reproduction failures especially in subjects with immune cell abnormalities and increased NK cell level and function. [ABSTRACT FROM AUTHOR]

We aimed to assess if Endoplasmic reticulum aminopeptidase 1 (ERAP1) polymorphisms might impress Human leukocyte antigen (HLA)-B27-free heavy chains (FHCs) expression on macrophages and eventually NK cell activation in Ankylosing spondylitis (AS). Blood samples were obtained from 10 HLA B27+ patients with protective and 10 HLA B27+ patients with non-protective genotype. Monocytes were isolated and polarized toward M1 and M2 macrophages. ERAP1 was inhibited in macrophages, which were then co-cultured with autologous NK cells. Expression of HLA-B27-FHCs on M1 and M2 macrophages was reduced in patients with protective ERAP1 genotype. Co-culturing ERAP1-inhibited M1 macrophages and NK cells from patients with protective genotype resulted in downmodulation of CD69 and CD107a markers on NK cells and reduced number of IFN-γ+ NK cells compared to that of patients with non-protective genotypes. Inhibition of ERAP1 activity, by diminishing NK activation, may have therapeutic value in treating AS patients. • Expression of HLA-B27-FHCs on M1 macrophages was reduced in patients with protective ERAP1 genotype. • ERAP1 inhibition in M1 macrophages downregulated HLA-B27-FHCs surface expression. • ERAP1 inhibited M1 macrophages downregulate CD69 and CD107a markers on NK cells in patients with protective genotype. • ERAP1 inhibited M1 macrophages led to lower development of IFN-γ + NK cells in patients with protective genotype. • Inhibition of ERAP1 activity, by diminishing NK activation, may have therapeutic value in treating AS patients. [ABSTRACT FROM AUTHOR]

There has been limited study on the impact of PBMC therapy in RSA patients with immunological disorders such as Th17 and Treg cell dysregulation, as well as their associated factors. This study aimed to assess the efficacy of PBMC therapy in modulating immune cell frequency, cytokine production, transcription factors, and miRNAs implicated in the regulation of their function, as well as their potential superiority to routine treatments. Fifty RSA women who had received PBMCs and 50 matched-paired control RSA women who had received the routine treatments were recruited and followed for three months. The frequencies of Th17, Treg, NK, and B cells were assessed using flow cytometry. Thereafter, the gene expression level of the transcription factors and related miRNAs of Treg cell and Th17 cell was quantified using RT-PCR. Then ELISA was employed to assess the cytokine production of Th17 and Treg cells. Finally, the live birth rate and miscarriage rate were evaluated as clinical outcomes in this study. Flow cytometry analysis revealed that PBMC therapy significantly reduces the frequencies of Th17 and NK cells while enhancing the frequency of Treg cells. RT-PCR analysis confirmed that PBMC therapy significantly downregulates RORγt and upregulates FoxP3. Likewise, RT-PCR analysis showed that PBMC therapy reduces the expression of miR-25, miR-155, and miR-326 while increasing the expression of miR-10a. ELISA results demonstrated that PBMC therapy considerably decreases the concentration of inflammatory cytokines IL-1β, IL-17, and TNF-α and enhances the concentration of anti-inflammatory cytokines IL-10 and TGF-β. Following PBMC therapy live birth rate raised while miscarriage rate reduced. Our findings suggested that, in contrast to routine treatments, PBMC therapy can significantly modulate the maternal immune system by enhancing the Treg/Th17 paradigm and regulating the expression of Treg and Th17 cell-associated cytokines, transcription factors, and miRNAs. This treatment also can increase the live birth rate in RSA patients. • LIT had superior immunomodulatory effects in RSA patients as compared to routine treatments. • LIT can effectively target the Treg/Th17 paradigm by directing the expression of cytokines, transcription factors, and miRNAs toward Treg cell immunodominance. • Many studies are still warranted to corroborate our findings and establish LIT as a viable therapeutic approach for RSA women. [ABSTRACT FROM AUTHOR]

The ongoing COVID-19 pandemic is still a challenging problem in the case of infection treatment. The immunomodulatory effect of Nanocurcumin was investigated in the present study in an attempt to counterbalance the immune response and improve the patients' clinical symptoms. 60 confirmed COVID-19 patients and 60 healthy controls enrolled in the study. COVID-19 patients were divided into Nanocurcumin and placebo received groups. Due to the importance of the role of NK cells in this disease, the frequency, cytotoxicity, receptor gene expression of NK cells, and serum secretion levels of inflammatory cytokines IL-1β, IL-6, TNF-α, as well as circulating C5a as a chemotactic factor an inflammatory mediator was evaluated by flow cytometry, real-time PCR and enzyme-linked immunosorbent assay in both experimental groups before and after the intervention. Given the role of measured factors in the progression and pathogenesis of COVID-19 disease, the results can help find appropriate treatments. The results of this study indicated that the Nanocurcumin could significantly increase the frequency and function of NK cells compared to the placebo-treated group. As an immunomodulatory agent, Nanocurcumin may be a helpful choice to improve NK cell function in COVID-19 patients and improve the clinical outcome of patients. [Display omitted] • Nanocurcumin could significantly increase the frequency and cytotoxicity of NK cell in COVID-19 patients. • Nanocurcumin could remarkably enhance the expression levels of activating receptors of NK cells in COVID-19 patients. • Nanocurcumin could notably reduce the expression levels of inhibitory receptors of NK cells in COVID-19 patients. • Nanocurcumin could meaningfully decline the serum levels of IL-1, IL-6, TNF-, and C5a in COVID-19 patients. • Nanocurcumin would be a potent therapeutic agent in SARS-CoV2 infection by augmenting the NK cell responses. [ABSTRACT FROM AUTHOR]

• Implantation failure is one of the factors contributing to pregnancy rate reduction after IVF. • Local immunological cells and factors at implantation site play an important role in pregnancy process. • PBMC-therapy has positive effect, by developing required initial inflammation for implantation. Infertility is one of the most common problems among couples worldwide. Recurrent pregnancy loss, premature ovarian failure, recurrent implantation failure and etc. are common high prevalence disorders in societies. We will review the definition, causes and treatment of recurrent implantation failure disorder in recent studies. Implantation refers to the attachment of the embryo to the endometrial luminal surface and recurrent implantation failure (RIF) is defined as the failure to achieve a pregnancy after transferring high-grade embryos through at least three in vitro fertilization (IVF) cycles to the endometrium. The embryo factors, maternal age, uterine factors, and multifactorial effectors have been considered as the causes of implantation failure. In this review, we aim to focus on immunological factors and cells such as pro-inflammatory cytokines and dendritic cells, macrophages, decidual and uterine NK cells, as well as Th-1 cells. There are different types of treatment according to the cause of RIF including aspirin and low-molecular-weight heparin therapy, immunosuppressive drugs, intravenous immunoglobulins, and hydroxychloroquine. Among immunological recurrent implantation failure therapy, we will discuss the intrauterine PBMC-therapy in detail. [ABSTRACT FROM AUTHOR]