CD200-dependent and nonCD200-dependent pathways of NK cell suppression by human IVIG

Effects of Intravenous Immunoglobulins on Human Innate Immune Cells: Collegium Internationale Allergologicum Update 2024

BACKGROUND

Intravenous immunoglobulin (IVIg) has been used for almost 40 years in the treatment of autoimmune and systemic inflammatory diseases. Numerous cells are involved in the innate immune response, including monocytes/macrophages, neutrophils, dendritic cells, mast cells, basophils, eosinophils, natural killer cells, and innate lymphoid cells. Many studies have investigated the mechanisms by which IVIg down-modulates inflammatory and autoimmune processes of innate immune cells. However, questions remain regarding the precise mechanism of action in autoimmune or inflammatory conditions. The aim of this work was to review the immunomodulatory effect of IVIg on only human innate immune cells. A narrative review approach was chosen to summarize key evidence on the immunomodulatory effects of commercially available and unmodified IVIg on human innate immune cells.

SUMMARY

Numerous different immunomodulatory effects of IVIg have been reported, with some very different effects depending on the immune cell type and disease. Several limitations of the different studies were identified. Of the 77 studies identified and reviewed, 29 (37.7%) dealt with autoimmune or inflammatory diseases. Otherwise, the immunomodulatory effects of IVIg were studied only in healthy donors using an in vitro experimental approach. Some of the documented effects showed disease-specific effects, such as in Kawasaki disease. Various methodological limitations have also been identified that may reduce the validity of some studies.

KEY MESSAGE

As further insights have been gained into the various inflammatory cascades activated in immunological diseases, interesting insights have also been gained into the mechanism of action of IVIg. We are still far from discovering all the immunomodulatory mechanisms of IVIg.

CD200R activation on naïve T cells by B cells induces suppressive activity of T cells via IL-24

CD200 is an anti-inflammatory protein that facilitates signal transduction through its receptor, CD200R, in cells, resulting in immune response suppression. This includes reducing M1-like macrophages, enhancing M2-like macrophages, inhibiting NK cell cytotoxicity, and downregulating CTL responses. Activation of CD200R has been found to modulate dendritic cells, leading to the induction or enhancement of Treg cells expressing Foxp3. However, the precise mechanisms behind this process are still unclear. Our previous study demonstrated that B cells in Peyer's patches can induce Treg cells, so-called Treg-of-B (P) cells, through STAT6 phosphorylation. This study aimed to investigate the role of CD200 in Treg-of-B (P) cell generation. To clarify the mechanisms, we used wild-type, STAT6 deficient, and IL-24 deficient T cells to generate Treg-of-B (P) cells, and antagonist antibodies (anti-CD200 and anti-IL-20RB), an agonist anti-CD200R antibody, CD39 inhibitors (ARL67156 and POM-1), a STAT6 inhibitor (AS1517499), and soluble IL-20RB were also applied. Our findings revealed that Peyer's patch B cells expressed CD200 to activate the CD200R on T cells and initiate the process of Treg-of-B (P) cells generation. CD200 and CD200R interaction triggers the phosphorylation of STAT6, which regulated the expression of CD200R, CD39, and IL-24 in T cells. CD39 regulated the expression of IL-24, which sustained the expression of CD223 and IL-10 and maintained the cell viability. In summary, the generation of Treg-of-B (P) cells by Peyer's patch B cells was through the CD200R-STAT6-CD39-IL-24 axis pathway.

Next generation of immune checkpoint molecules in maternal-fetal immunity

Successful pregnancy is a unique situation requires the maternal immune system to recognize and tolerate a semi-identical fetus and allow normal invasion of trophoblast cells. Although efforts have been made, the deep mechanisms of the maternal-fetal crosstalk have not yet been fully deciphered. Immune checkpoint molecules (ICMs) are a group of negative modulators of the immune response that avoid immune damage. They have been extensively studied in the fields of oncology and transplantation, while the latest evidence suggests that they are closely associated with pregnancy outcomes via multiple inhibitory mechanisms. Although studies have mostly demonstrated the regulatory role of the well-known PD-1, CTLA-4 at the maternal-fetal interface, what is unique about the newly discovered multiple ICMs remains a mystery. Here, we review the latest knowledge on ICMs, focusing on the first generation of checkpoints (PD-1, CTLA-4) and the next generation (Tim-3, Tigit, Lag-3, VISTA) highlighting their immunoregulatory roles in maternal-fetal tolerance and decidual vascular remodeling, and their involvement in pathological pregnancies. The content covers three aspects: the characteristics they possess, the dynamic expression profile of their expression at the maternal-fetal interface, and their involvement in pathological pregnancy. In immunotherapy strategies for pregnancy complications, upregulation of immune checkpoints may play a role. Meanwhile, the impact on pregnancy outcomes when using ICMs in clinical cancer treatment during pregnancy is a topic worth exploring. These may serve as a guide for future basic research and clinical applications of maternal-fetal immunity.

Regulation of the innate immune cells during pregnancy: An immune checkpoint perspective

The foetus can be regarded as a half‐allograft implanted into the maternal body. In a successful pregnancy, the mother does not reject the foetus because of the immune tolerance mechanism at the maternal‐foetal interface. The innate immune cells are a large part of the decidual leukocytes contributing significantly to a successful pregnancy. Although the contributions have been recognized, their role in human pregnancy has not been completely elucidated. Additionally, the accumulated evidence demonstrates that the immune checkpoint molecules expressed on the immune cells are co‐inhibitory receptors regulating their activation and biological function. Therefore, it is critical to understand the immune microenvironment and explore the function of the innate immune cells during pregnancy. This review summarizes the classic immune checkpoints such as PD‐1, CTLA‐4 and some novel molecules recently identified, including TIM‐3, CD200, TIGIT and the Siglecs family on the decidual and peripheral innate immune cells during pregnancy. Furthermore, it emphasizes the role of the immune checkpoint molecules in pregnancy‐associated complications and reproductive immunotherapy.

Reproductive outcomes of women with recurrent pregnancy losses and repeated implantation failures are significantly improved with immunomodulatory treatment

This study investigated if immunomodulatory treatment improves the in-vitro fertilization (IVF) success rates of women with two or more recurrent pregnancy losses (RPL) and repeated implantation failures (RIF) with cellular immune abnormalities and thrombophilia. We performed a retrospective cohort study of 197 RPL patients who received immunomodulatory and anticoagulation treatment undergoing IVF cycles (fresh or frozen embryo transfer). Patients were divided into four groups; Group 1: women with RPL but without RIF, Group 2: women with RPL and RIF (≥3), Group 3: women with RPL after IVF cycles (>2) and without RIF, and Group 4: women with RPL after IVF cycles and RIF. Patients received immunomodulatory treatment with prednisone-only or prednisone and intravenous immunoglobulin G (IVIG) and anticoagulation treatment with low molecular weight heparin and low dose aspirin. IVF success rates of study groups were compared to those of the historical controls. The pregnancy rate of IVF cycles with immunomodulatory treatment was significantly increased in all patients (48.2 % vs. 33.0 %, P < 0.001), Group 1 (54.2 % vs. 30.5 %, P < 0.005) and Group 2 (33.3 % vs. 11.0 %, P < 0.005) as compared to historical controls. The live birth rates per ET cycle were significantly improved for all patients (1.8 % vs. 39.6 %, P < 0.001), and study groups compared to their historical controls (Group 1, 43.1 % vs. 0 %; Group 2, 33.3 % vs. 2.5 %; Group 3, 45.5 % vs. 2.3 %; and Group 4, 16.7 % vs. 1.2 %, P < 0.001, respectively). Immunomodulatory and anticoagulation treatment significantly improved the reproductive outcomes of IVF cycles in women with a history of RPL and/or RIF of immune etiologies.

High Dose Intravenous IgG Therapy Modulates Multiple NK Cell and T Cell Functions in Patients With Immune Dysregulation

Intravenous immunoglobulin (IVIG) is an effective immunomodulatory treatment for immune dysregulation diseases. However, the mechanisms by which it reduces systemic inflammation are not well understood. NK cell cytotoxicity is decreased by IVIG in women with reduced fertility, but IVIG effects on NK cells in immune dysregulation are less clear. We hypothesized that IVIG modulation of lymphocyte function, especially in NK cells, is important for resolution of inflammation. Our aim was to identify IVIG-induced changes in a cohort of patients with Kawasaki disease (KD) and those that occur broadly in pediatric patients with various immune dysregulatory diseases. Peripheral blood mononuclear cells (PBMCs) of patients with KD or autoimmune/inflammatory diseases were phenotyped pre and post high dose IVIG treatment by flow cytometry. In KD patients, after IVIG infusion T_reg cell frequency and the proportion of activated CD25⁺ immunoregulatory CD56^bright NK cells was increased, and multiple lymphocyte subsets showed increased expression of the lymphoid tissue homing receptor CD62L. Importantly, IVIG treatment decreased the frequency of cells expressing the degranulation marker CD107a among cytotoxic CD56^dim NK cells, which was reflected in a significant reduction in target cell killing and in decreased production of multiple pro-inflammatory mediators. Interestingly, the activating receptor CD336 was expressed on a higher proportion of CD56^bright NK cells after IVIG in both KD and autoimmune/inflammatory patients while other NK receptors were increased differentially in each cohort. In autoimmune/inflammatory patients IVIG induced the proliferation marker CD71 on a higher percentage of CD56^dim NK cells, and in contrast to KD patients, CD107a⁺ cells were increased in this subset. Furthermore, when PBMCs were stimulated ex vivo with IL-2 or Candida antigen in autologous plasma, more of the CD4⁺ T cells of KD patients expressed CD25 after IVIG therapy but fewer cytotoxic T cells were degranulated based on CD107a expression. In summary, IVIG treatment in patients with immune dysregulation has multiple effects, especially on NK cell subsets and CD4⁺ T cells, which are compatible with promoting resolution of inflammation. These novel findings provide insight into the immunomodulatory actions of IVIG in autoimmune and inflammatory conditions.

CD200:CD200R Interactions and Their Importance in Immunoregulation

The molecule CD200, described many years ago as a naturally occurring immunomodulatory agent, capable of regulating inflammation and transplant rejection, has attracted additional interest over the past years with the realization that it may also serve as an important marker for progressive malignancy. A large body of evidence also supports the hypothesis that this molecule can contribute to immunoregulation of, among other diseases, infection, autoimmune disease and allergy. New data have also come to light to characterize the receptors for CD200 (CD200R) and their potential mechanism(s) of action at the biochemical level, as well as the description of a novel natural antagonist of CD200, lacking the NH₂-terminal region of the full-length molecule. Significant controversies exist concerning the relative importance of CD200 as a ligand for all reported CD200Rs. Nevertheless, some progress has been made in the identification of the structural constraints determining the interaction between CD200 and CD200R, and this information has in turn proved of use in developing novel small molecule agonists/antagonists of the interaction. The review below highlights many of these newer findings, and attempts to place them in the broad context of our understanding of the role of CD200-CD200R interactions in a variety of human diseases.

Is there a Role of Intravenous Immunoglobulin in Immunologic Recurrent Pregnancy Loss?

Recurrent pregnancy loss (RPL) commonly refers to three or more miscarriages that occur before 20 weeks of pregnancy. The immunological cause of RPL could be either an auto- or alloimmune-related event or both. Because of the discovery of immunological abnormalities in RPL patients in clinical practice, several immunomodulatory therapies were introduced to maintain the immune balance at the maternal-fetal interface. Intravenous immunoglobulin (IVIg) is one of the immunomodulators. In recent years, several studies have analyzed the therapeutic effect of IVIg on RPL patients with antiphospholipid syndrome (APS) or unexplained RPL. However, their results are controversial. IVIg can be used in RPL patients with APS who have previously failed in other treatments. It is recommended that IVIg infusion could be considered used before conception in RPL patients who have cellular immune abnormalities such as increased natural killer (NK) cell counts, NK cell cytotoxicity, or increased T helper (Th)1/Th2 ratio, depending on the cut-off values of each hospital. The aim of this review was to summarize the mechanisms, efficacy, pharmacokinetics, and side effects associated with passive immunization using IVIg in immunologic RPL, according to the literature published in recent years. We hope that more obstetricians will be able to understand the timing and indication of IVIg properly in immunologic RPL patients and effectively enhance pregnancy outcomes for mothers and neonates.

Clinical Significance of CD200 and CD56 Expression in Patients with Acute Myeloid Leukemia

BACKGROUND

Acute myeloid leukemia (AML) escape from immunosurveillance by immunosuppression. CD200 and CD56 expression represented an independent prognostic factor in many hematological malignancies but its importance in AML patients remains to be identified.

METHODS

CD200 and CD56 expression were assessed in the bone marrow blasts for Fifty-two (52) newly diagnosed AML by flowcytometry before start of therapy.

RESULTS

CD200+ expression was reported in 28.8% of patients while 17.3% of patients showed CD56+ expression. M4 FAB revealed high frequency of both CD200+ and CD56+ expression. The overall survival of CD200+ patients was 19.2% compared to 35.3% in CD200- (P= 0.049). On the other hand, CD56+ patients had the lowest complete remission rate (22.2% vs. 53.4%). In addition, CD56+ population had significant bad influence on overall survival than those of CD56- population (11.1 % vs. 35.5 %, P= 0.047).

CONCLUSIONS

CD200 and CD56 positive expression by myeloblasts at diagnosis denote poor prognostic indicator and correlated with poor cytogenetic findings. CD200 could be used as therapeutic target in AML.<br />.

Mesenchymal Stromal Cells from Fetal and Maternal Placenta Possess Key Similarities and Differences: Potential Implications for Their Applications in Regenerative Medicine

Placenta-derived mesenchymal stromal cells (MSC) have attracted more attention for their immune modulatory properties and poor immunogenicity, which makes them suitable for allogeneic transplantation. Although MSC isolated from different areas of the placenta share several features, they also present significant biological differences, which might point to distinct clinical applications. Hence, we compared cells from full term placenta distinguishing them on the basis of their origin, either maternal or fetal. We used cells developed by Pluristem LTD: PLacenta expanded mesenchymal-like adherent stromal cells (PLX), maternal-derived cells (PLX-PAD), fetal-derived cells (PLX-R18), and amniotic membrane-derived MSC (hAMSC). We compared immune modulatory properties evaluating effects on T-lymphocyte proliferation, expression of cytotoxicity markers, T-helper and T-regulatory cell polarization, and monocyte differentiation toward antigen presenting cells (APC). Furthermore, we investigated cell immunogenicity. We show that MSCs and MSC-like cells from both fetal and maternal sources present immune modulatory properties versus lymphoid (T cells) and myeloid (APC) cells, whereby fetal-derived cells (PLX-R18 and hAMSC) have a stronger capacity to modulate immune cell proliferation and differentiation. Our results emphasize the importance of understanding the cell origin and characteristics in order to obtain a desired result, such as modulation of the inflammatory response that is critical in fostering regenerative processes.

Treatment with intravenous immunoglobulin in patients with recurrent pregnancy loss: An update

Intravenous immunoglobulin (IVIg) has a documented clinical effect in many autoimmune diseases and has so far been tested in >10 randomised controlled trials (RCTs) in women with recurrent pregnancy loss (RPL). The results of the RCTs have, however, been very divergent. In meta-analyses of all trials, no significant impact on live birth rate has been reported. In contrast, in sensitivity analyses, IVIg significantly increased live birth rates when initiated prior to conception and it had a borderline significant therapeutic effect in women with secondary RPL. Higher dosages of IVIg and serological signs of autoimmunity in the treated patients tended to increase the success rate after treatment. A follow-up study of patients from our recent RCT also supports a significant therapeutic effect in patients who had received IVIg before conception. The lessons learned from the published trials and meta-analyses should be incorporated in the design of future RCTs of IVIg in the treatment of RPL.

Intravenous immunoglobulin G in women with reproductive failure: The Korean Society for Reproductive Immunology practice guidelines

The task force of the Korean Society for Reproductive Immunology recommends intravenous immunoglobulin G treatment in women with reproductive failure, including recurrent pregnancy loss and/or repeated implantation failure, who show cellular immune factors such as abnormal natural killer cell levels, natural killer cell cytotoxicity, and/or type 1 T helper immunity.

CD200:CD200R-Mediated Regulation of Immunity

The type 1 membrane glycoprotein CD200, widely expressed on multiple cells/tissues, uses a structurally similar receptor (CD200R1), whose expression is more restricted to cells of the myeloid and lymphoid lineages, to transmit signals affecting responses in multiple physiological systems. Thus CD200 expression is reported to exert effects on cancer growth, autoimmune and allergic disorders, infection, transplantation, bone development and homeostasis, and reproductive biology. It was initially thought, based on the idea that CD200R1 was mostly expressed on cells of myeloid origin, that CD200:CD200R1 interactions were primarily dedicated to controlling myeloid cell function. However additional members of the CD200R family have now also been identified, although their function(s) remain unclear, and CD200R1 itself is now known to be expressed by subsets of T cells and other cells. Together these observations add layers of complexity to our understanding of CD200-related regulation. In common with a number of physiological systems, the mechanism(s) of CD200-induced signaling seem to fit within a similar framework of opposing actions of kinases and phosphatases. This paper highlights the advances in our knowledge of immunoregulation achieved following CD200:CD200R interaction and the potential clinical applicability of that information.

A high dose intravenous immunoglobulin therapy for women with four or more recurrent spontaneous abortions

Recurrent spontaneous abortion (RSA) may have immunological etiology. The aim of this study was to assess the efficacy of a high dose intravenous immunoglobulin (HIVIg) therapy, in which 20 g of intact type immunoglobulin was infused daily for 5 days during early gestation, for women who had a history of four or more consecutive spontaneous abortions of unexplained etiology. A total of 60 pregnant RSA women underwent HIVIg therapy, and the pregnancy outcome was assessed. The live birth rate was 73.3% (44/60). Fifteen pregnancies ended in spontaneous abortion, and one ended in intrauterine fetal death. In 11 of the 15 spontaneous abortions, fetuses had abnormal chromosome karyotype. When the 11 pregnancies with abnormal chromosome karyotype were excluded, the live birth rate was as high as 89.8% (44/49). The HIVIg therapy may be effective for severe cases of unexplained RSA.

NK cells, autoantibodies, and immunologic infertility: a complex interplay

Infertility and recurrent spontaneous abortion (RSA) are heterogeneous conditions that have been frequently explained with an immunological pathomechanism. A deeper insight into apparently unexplained infertility and RSA shows increasing evidences supporting both alloimmune and autoimmune mechanisms, in which natural killer (NK) cells and autoantibodies seem to play a relevant role. Successful pregnancy is considered as Th1-Th2 cooperation phenomenon, with a predominantly Th2-type lymphocytes response, together with the emerging role of interleukin (IL)-12, IL-15, and IL-18 and of other unidentified soluble factors dependent on NK cells. Uterine NK cells comprise the largest population at implantation site, and their activity, characteristics, and abundance suggest that they participate at the "decidualization" process that, vice versa, induces NK activation and recruitment in each menstrual cycle. However, NK cell alteration may be associated with impaired pregnancy, and the modulation in the number of circulating NK cells is most likely to be a primary event rather than an active inflammation/drug administration consequence during an inflammatory/autoimmune process, thus playing an important role in the pathogenesis of immunological infertility. Relationships within immunological infertility, recurrent spontaneous abortion, autoantibodies, and NK cells will be reviewed herein.

CD3-CD56+CD16+ natural killer cells and improvement of pregnancy outcome in IVF/ICSI failure after additional IVIG-treatment

PROBLEM

The purpose of this retrospective, observational study was to investigate whether additional treatment with intravenous immunoglobulin (IVIG) increased the rate of successful pregnancies after repeated implantation failure (RIF). The retrospective data were compared with data of patients without IVIG-therapy from the meta-analysis of Clark et al.

METHOD OF STUDY

A total of 188 women with 226 treatment cycles between 2007 and 2009 were evaluated for IVIG therapy. The percentage of NK cells was measured two times before a new embryo transfer (only women with NK cell percentages >12% were included) and after embryo transfer at a positive pregnancy test.

RESULTS

In comparison with the meta-analysis of Clark et al., we observed a pregnancy rate of 50.5%, an implantation rate of 21% and a miscarriage rate of 16.8%. In 42%/IVIG- patient or 34.9%/embryo transfer, we observed a live born baby. The live born rate per embryo was 16.6%. In accordance with the study of Kwak et al., we indicate a decrease in the NK cells in patients with improved pregnancy outcome.

CONCLUSION

In a subgroup of RIF-patients with high level of CD56(+) CD16(+) NK-cells the additional application of IVIG leads to a favourable pregnancy outcome.