Two-way calf to dam major histocompatibility class I compatibility increases risk for retained placenta in cattle

Citation
Benedictus L, Thomas AJ, Jorritsma R, Davies CJ, Koets AP. Two‐way calf to dam major histocompatibility class I compatibility increases risk for retained placenta in cattle. Am J Reprod Immunol 2012; 67: 224–230 Problem In cattle, retained placenta (RP) is suggested to arise from failure of immune‐mediated rejection of the fetal membranes by the maternal immune system and is associated with major histocompatibility (MHC) class I compatibility between calf and dam. Method of study To study the association between RP and different MHC class I compatibilities between calf–dam–granddam combinations, massively parallel pyrosequencing was used to determine the MHC class I haplotypes of cows with and without RP. Results Two‐way calf to dam MHC class I compatibility gave a high risk for RP. There was a tendency for a higher risk for RP with calf to dam MHC class I compatibility. Conclusions We concluded that in two‐way compatible pregnancies, the maternal immune system fails to reject the fetal membranes, and the fetal immune system does not mount an immune response against maternal MHC class I antigens that could influence the immune‐mediated rejection of the fetal membranes by the maternal immune system. The lack of immune‐mediated rejection of the fetal membranes by the maternal immune system increases the risk of occurrence of RP.     

Stress-Triggered Abortion in Mice Prevented by Alloimmunization

PROBLEM: To determine if immunotherapy can prevent abortion triggered by mechanisms that in humans may be treatable by psychotherapy. METHOD: The effects of alloimmunization against paternal strain antigens were tested in pregnant mice subjected to stress. RESULTS: Restraint stress boosted the resorption rate assessed on day 13.5 of pregnancy in DBA/2-mated C3H/HeJ mice with an optimal effect on day 4.5 of pregnancy, and premating alloimmunization greatly reduced the effect. By contrast, CBA/J and A/J mice proved resistant to abortion boosting by restraint stress. A/J mice mated to DBA/2 or C3H/HeJ males showed reduced fertility, perhaps due to failure of pregnancy immediately after the stress, but this was not corrected by alloimmunization with either DBA/2 [class I + class II major histocompatibility complex (MHC) immunogen] or C3H/HeJ (class I MHC immunogen) splenocytes. There was a reduction in the endogenous resorption rate, however, and implantation number was slightly increased by preimmunization using DBA/2 cells. The abortion rate could be boosted, however, by ultrasonic noise stress of high abortion rate CBA/J, and preimmunization using BALB/c (H-2^d) splenocytes protected. A similar boosting of loss in low abortion rate BALB/k mice was ameliorated (albeit not completely) by preimmunization with allogeneic paternal but not syngeneic splenocytes. CONCLUSIONS: Immunotherapy may protect against a variety of potential triggers of spontaneous abortion, including those that may be amenable to psychological remedies, and possible mechanisms are discussed.     

Implantation site in normal pregnancy. A study with monoclonal antibodies.

In the present study, the presence of major histocompatibility complex antigens (MHC) and the degree and nature of inflammatory response in the human placenta were determined by staining frozen tissue sections with monoclonal antibodies and an immunoperoxidase technique. Although class I (HLA-A, B, and C) and Class II (HLA-DR, Ia-like) MHC antigens were not demonstrated in the syncytiotrophoblast, Class I antigens were found in trophoblast of the placental septum, shell, and implantation site and in the chorionic villous stroma. There was no staining for Ia-like antigens in the fetal components of the placenta. T cells were scarce and evenly scattered in the normal implantation site. No T cells infiltrated the chorionic villi. B cells and natural killer cells were not identified in the human placenta. Macrophages constituted more than 20% of the decidual cells and had morphologic features identical to those of "small decidual cells." The lack of T-cell infiltration of the fetal placental structures and their scarcity in the implantation site support the notion that T-cell-mediated immune response against placental antigens is not generated by the maternal host in normal pregnancy. The abundance of macrophages at the implantation site may be related to their possible role in the suppression of immune response.     

Production of Embryotoxic IgG Antibodies During IFN-γ Treatment of Pregnant Mice

PROBLEM: Administration of IFN-γ during pregnancy in mice is deleterious not only to fetal survival but also to maternal physiology. Thus, injection of recombinant IFN-γ from days 6–11 of gestation results in significant increase of fetal abortion, decrease of fetal weight accompanied by morphological defects of the embryo, and induction of class II MHC antigens on the spongiotrophoblast zone of the placenta. At the maternal level, this treatment causes splenomegaly, decrease of hematocrit levels, and increase of IgG production. In an attempt to dissect out the different phenomena observed, we examined the properties of polyclonal IgG antibodies contained in the animals' serum as to their ability to recognize antigenic determinants on IFN-γ-induced placentae and isolated trophoblasts. METHOD: Serum from IFN-γ-treated pregnant mice was tested in vitro for its ability to recognize specific structures on primary trophoblasts and placental sections induced by IFN-γ. In vivo this serum was injected in pregnant mice, and the outcome of pregnancy was evaluated. Monoclonal antibodies, resulting from the fusion of spleen cells from IFN-γ-treated pregnant mice to a myeloma cell line, were used to certify the IgG-dependent embryotoxic effects observed with the polyclonal serum. RESULTS: It was demonstrated that both the polyclonal serum and the monoclonal antibodies recognize antigenic determinants only on the IFN-γ-induced trophoblasts, placentae, and embryos, reduce fetal size, and cause splenomegaly in the mother, but do not affect the percentage of abortions as compared to controls. CONCLUSIONS: IFN-γ induces specific protein(s) on trophoblasts, which are responsible for embryotoxic antibody production in the mother. Since human abortion has been correlated with the production of embryotoxic IgG antibodies, this animal model may prove to be a useful tool in the analysis of events leading to pregnancy loss.     

Placental Tissue From Human Miscarriages Expresses Class II HLA-DR Antigens

PROBLEM : Class II major histocompatibility antigens occupy a central role in the development of humoral or cellular immunologic responses. Surprisingly, in the maternal-fetal interphase, where two genetically different organisms come in direct contact, these antigens are absent. Based on previous studies in mice we have demonstrated that the absence of class II antigens represents another mechanism of fetal protection from the maternal immune response and, furthermore, that the induction of these antigens in the placenta makes the tissue immunogenic and susceptible to maternal immune attack, leading thus to fetal abortion. In order to test this hypothesis in humans, we analyzed the presence of class II antigens in aborted placentae. METHOD : Class II expression on aborted placentae was examined by immunoperoxidase staining on frozen sections. We also studied hematologic changes that accompany such events, measuring white and red blood cell counts, hematocrit, hemoglobin, as well as IgG serum levels by standard techniques. RESULTS : The detection of class II antigens on the aborted tissue indicates that these antigens are indeed major components of a pathway, which leads to a plethora of abnormal phenomena for the maternal organism such as low hematocrit levels, elevated IgG production, and increase of white blood cell numbers. CONCLUSION : The results presented are consistent with our previous observations in mice and point to novel directions not only to pregnancy failure diagnosis, but also to new therapeutic approaches.     

IFN-gamma facilitates release of class II-loaded intracellular pools in trophoblast cells: a novel property independent of protein synthesis.

Interferon-gamma (IFN-gamma) is an abortion-inducing factor, yet its effects in such a reaction are subject to various levels of regulation. The trophoblast cell line TROPHO-1 can be induced by IFN-gamma to express mRNA and surface class II major histocompatibility complex (MHC) proteins after 8 and 48 h of stimulation, respectively. Untreated cells, however, show an intracellular accumulation of class II antigens earlier (6 h), indicating the existence of MHC pools in the cystosol independent of any induction. On addition of IFN-y, immunofluorescence, subcellular fractionation, and ELISA experiments showed that class II antigen activity detected in the endosomal compartments of the cells could be measured in the culture supernatants. These soluble class II proteins, when isolated and purified using magnetic bead isolation techniques and tested in SDS-PAGE gel and Western blot experiments, had a molecular weight of 70 kDa. Administration of these molecules to pregnant mice as culture supernatants increased the abortion rate and decreased maternal hematocrit levels, effects that could be immunoabsorbed by anti-I-A(d) monoclonal antibodies (mAb). These results indicate that although surface class II molecules are not expressed on trophoblast cells, they accumulate in endosomal compartments and can be released from the cells on addition of IFN-gamma. This new IFN-gamma property, to mobilize intracellular pools of class II MHC antigens in trophoblast cells independent of de novo protein synthesis and induce their release to the extracellular matrix, is a mechanism that appears to be involved in the fetal rejection process, facilitating priming of the maternal organism against the fetal allograft.     

Maternal cell traffic bounds for immune modulation: tracking maternal H-2 alleles in spleens of baby mice by DNA fingerprinting

We have previously reported that the immunization of pregnant mice with T-dependent antigens successfully induced suppression of the antigen-specific plaque-forming cell (PFC) response to the relevant antigens in the offspring. This suppression was not caused by the administered antigens, the antibodies produced by the pregnant mother, or lactational transfer, but was dependent on the presence of the intact maternal T cells. It was major histocompatibility complex (MHC)-restricted manner tolerance, which continued for at least one-sixth of the murine life. Traditionally, the placenta acts as a natural barrier, not allowing the cells to pass through. However, the results presented strongly suggested that maternal T cells pass through the placenta and subsequently induce tolerance. In this present study, we attempted to substantiate the presence of maternal cells in the fetal circulation through the use of molecular techniques. We found that a highly polymorphic microsatellite sequence within the class II Eb gene of the H-2 complex is useful for the molecular detection of various H-2 alleles. DNA polymorphic analysis was used for tracking maternal H-2 alleles in the spleens of baby mice. The main procedure involved polymerase chain reaction amplification and restriction fragment length polymorphism analysis of the DNA sequence encompassing the H-2-specific microsatellite from the genomic DNA of baby mice. The results indicated that maternal T cells of immunized pregnant mice cross the placenta into the fetus, eventually inducing antigen-specific immunological tolerance in the offspring.     

The maternal-fetal relationship in human pregnancy: an immunogenetic perspective.

Although the mechanisms by which the fetal allograft escapes rejection are still poorly understood, abundant evidence has accumulated suggesting multiple roles for major histocompatibility complex (MHC) genes in pregnancy. Specific maternal MHC genotypes and maternal-fetal histocompatibility have been associated with recurrent spontaneous abortion, decreased fecundity, segregation distortions, altered sex ratios, fetal growth rates, and maternal autoimmune disease progression. In this review, the evidence for a variety of MHC gene effects in human pregnancy is considered.     

Localization of fetal major histocompatibility complex antigens and maternal leukocytes in murine placenta. Implications for maternal-fetal immunological relationship

An immunohistochemical study of the days 14-19 murine placenta and uterus using a panel of antibodies specific for maternal and paternal class I major histocompatibility complex (MHC) antigens, specific leukocyte subsets, and other lineage-specific markers was performed to elucidate the nature of the maternal tolerance of the fetal implant in the uterus. Fetally derived trophoblast lining maternal blood spaces lacked MHC antigens, but other interstitial trophoblasts expressed fetally derived polymorphic class I MHC determinants. The latter class I MHC-bearing trophoblasts were most prominent in the maternal decidua basalis where they were mixed with maternal cells. Our results identify two factors that may be relevant for understanding why these alloantigen-bearing fetal cells are not rejected by the mother: a paucity of la-bearing antigen presenting cells, macrophages, and mature T and B lymphocytes and the presence of large numbers of Thy-1+ asialo-GM-1+ CD4- CD8- bone marrow-derived (CLA/Ly5+) cells of maternal origin in the decidua basalis. These latter cells correspond to previously described granulated metrial gland cells that may be involved in local immunoregulation.     

Induction of mouse syngeneic MLR by in vivo xenogeneic immunization with HLA-DR antigens

To study in mice the effects of in vivo xenogeneic immunization with human major histocompatibility complex (MHC) class II antigens, the animals were injected with HLA-DR antigens and their proliferative responses tested in vitro. The results showed that small amounts of HLA-DR proteins, acting as nominal antigens, were not only able to prime mice for a secondary in vitro xenogeneic mixed lymphocyte reaction but also induced a syngeneic mixed lymphocyte reaction. In contrast, allogeneic or syngeneic immunization of mice with soluble MHC class II molecules failed to stimulate an autoreactive response. The syngeneic mixed lymphocyte reaction was primarily directed against syngeneic MHC class II molecules since the murine T lymphocytes reacted against MHC class II-positive dendritic spleen cells and MHC class II-transfected mouse fibroblasts. A self-reactive T-cell line induced under these experimental conditions did not react in xenogeneic and allogeneic mixed lymphocyte reactions. However, these T lymphocytes proliferated when human peripheral blood lymphocytes of various haplotypes were presented in the context of syngeneic mouse antigen presenting cells.     

Pathogenesis of bovine neosporosis

The protozoan parasite Neospora caninum is a major pathogen of cattle and dogs, being a significant cause of abortion in cattle in many countries. It is one of the most efficiently transmitted parasites, with up to 90% of cattle infected in some herds. The pathogenesis of abortion due to Neospora is complex and only partially understood. Losses occur after a primary infection during pregnancy but more commonly as the result of recrudescence of a persistent infection during pregnancy. Parasitaemia is followed by invasion of the placenta and fetus. It is suggested that abortion occurs when primary parasite-induced placental damage jeopardises fetal survival directly or causes release of maternal prostaglandins that in turn cause luteolysis and abortion. Fetal damage may also occur due to primary tissue damage caused by the multiplication of N. caninum in the fetus or due to insufficient oxygen/nutrition, secondary to placental damage. In addition, maternal immune expulsion of the fetus may occur associated with maternal placental inflammation and the release of maternal pro-inflammatory cytokines in the placenta. Thus N. caninum is a primary pathogen capable of causing abortion either through maternal placental inflammation, maternal and fetal placental necrosis, fetal damage, or a combination of all three. The question of how N. caninum kills the fetus exposes the complex and finely balanced biological processes that have evolved to permit bovine and other mammalian pregnancies to occur. Defining these immunological mechanisms will shed light on potential methods of control of bovine neosporosis and enrich our understanding of the continuity of mammalian and protozoal survival.     

Evolution of the MHC: antigenicity and unusual tissue distribution of Xenopus (frog) class II molecules

Antibodies that recognize Xenopus class II molecules have been developed. Mouse monoclonal antibodies were prepared by immunizing BALB/c mice with frog MHC antigens that had been partially purified with alloantisera, and by immunizing mouse spleen cells in vitro with activated Xenopus T lymphocytes. In addition, five mouse monoclonal antibodies specific for human class II antigens were found to cross-react with Xenopus class II antigens. A.TH mice, which do not express E class II molecules, always produce immunoprecipitating antibodies reactive with frog class II molecules after immunization with frog lymphocytes; other mouse strains rarely produce such antibodies. Two of the monoclonal antibodies raised against frog class II molecules recognize the denatured class II beta chain on Western blots, and the other three appear to recognize only the class II heterodimeric complex. The antibodies display differential reactivity with the allelic class II products of Xenopus. The monoclonal antibodies react with all adult lymphocytes in the spleen and peripheral blood, T cells and B cells having equivalent levels of class II antigens per cell. Class II molecules are "differentiation antigens" on adult thymocytes as the expression is greatest on the mature medullary population. The number of class II molecules/lymphocyte increases after culturing in medium containing fetal bovine serum. Sequential immunoprecipitation and isoelectric focusing experiments have shown that cell surface class II molecules immunoprecipitated with the monoclonal antibodies are the same as those immunoprecipitated with the cross-reactive antiserum specific for DR antigens which was previously used to identify frog class II molecules.     

Autoreactivity to self H-2Kb peptides in TAP1 mice. Intravenous administration of H-2Kb class I-derived peptides induces long-term survival of grafts from C57BL/6 donors

We and others have previously shown that TAP1-/- mice (H-2b) reject grafts from donors without major histocompatibility complex (MHC) disparity that express wild-type levels of H-2b class I molecules (C57BL/6, TAP1+/+ mice). In this same model, we also showed that subcutaneous priming of TAP1-/- mice with synthetic peptides derived from the H-2Kb molecule accelerated graft rejection and that in vivo depletion of CD4+ T cells induced a significant prolongation of graft survival, suggesting an important role for CD4 T cells. We hypothesize that, in this model, rejection is triggered by the recognition of class I molecules or derived peptides, in an inflammatory microenvironment, by a functionally altered autoreactive T-cell repertoire that escapes the control of peripheral regulatory mechanisms. In the present study, we analysed the cellular autoreactivity induced by synthetic peptides derived from the H-2Kb sequence in naive and TAP1-/- mice transplanted with C57BL/6 grafts, and investigated whether intravenous modulation of autoreactivity to these peptides induced transplantation tolerance. We showed that TAP1-/- mice have peripheral autoreactive T cells that recognize H-2Kb peptides. A significant amplification of proliferation against these peptides was detected in TAP1-/- mice that rejected grafts, indicating that the inflammatory context of transplantation induced peripheral expansion of these autoreactive T cells. Furthermore, intravenous injection of H-2Kb-derived peptides significantly prolonged graft survival in some animals. In these mice (> 100 days graft survival), we observed intragraft inhibition of interferon-gamma and interleukin-10 expression, suggesting that these cytokines have an active role during the rejection. In conclusion, our present data indicate that inflammatory autoreactive T cells directed against H-2Kb peptides can be inhibited in the periphery to prolong graft survival in TAP1-/- mice.     

Mechanisms of Fetal Demise in Pregnant Mice Immunized to Murine Alpha-Fetoprotein

ABSTRACT: Nya: NYLAR mice were immunized to murine alpha-fetoprotein (AFP) by active immunization with rat AFP in Freund's adjuvant emulsion before mating or by passive immunization with a high or low dose of whole rabbit antimouse AFP serum or rabbit anti-AFP IgG at 8–20 days of gestation. In the passively immunized group, anti-AFP serum or purified anti-AFP IgG administered at the end of the second week of gestation produced abortion after 24 hours of 41 and 48% of fetuses, respectively. Although abortion did not occur in the low-dose group, the anti-AFP serum produced fetal death in 32%, as did the anti-AFP IgG in 26%, in 72 hours. In the actively immunized group rat AFP produced developmental arrest, but not abortion, in mothers bearing autologous antibodies to mouse AFP. Histopathologic analysis revealed that fetal death resulted from separation of fetal and maternal tissues of the placenta due to subplacental hemorrhages. Immunofluorescent localization of the rabbit IgG implicated both the chorioallontois and yolk sac placenta as target tissues.     

HLA-G-mediated NK cell senescence promotes vascular remodeling： implications for reproduction

The uterus in early pregnancy is a non-lymphoid organ that is enriched in natural killer （NK） cells. Studies to address the role of these abundant human NK cells at the maternal/fetal interface have focused on their response to the major histocompatibility complex （MHC） molecules on fetal trophoblast cells that they contact. The interaction of maternal NK cell receptors belonging to the killer cell immunoglobulin-like receptor （KIR） family with trophoblast MHC class I molecules in pregnancy can regulate NK cell activation for secretion of pro-angiogenic factors that promote placental development. This review will cover the role of KIR at the maternal/fetal interface and focus on KIR2DL4, a KIR family member that is uniquely poised to play a role in pregnancy due to the restricted expression of its ligand, human leukocyte antigen （HLA）-G, by fetal trophoblast cells early in pregnancy. The pathways by which KIR2DL4-HLA-G interactions induce the cellular senescence of NK cells and the role of the resulting senescence-associated secretory phenotype （SASP） in vascular remodeling will be discussed in the context of reproduction.     

Restricted blocking of cytotoxic T-cell function by anti-H-2K/D antibodies

Antibodies specific for H-2K and H-2D, the murine major histocompatibility complex (MHC)-encoded class I antigens, can block cytotoxic T (Tc)-cell function. Antibodies specific for the Tc cell and not the target cell have been used to map inhibition to the effector cell, suggesting a role for class I antigens in Tc-cell function. These antibody effects have been demonstrated for both alloreactive and MHC-restricted Tc cells, but inhibition has only been revealed by measuring cytotoxicity in a short-term assay. Using the neutral red assay for cytotoxicity, blocking effects evident after a 1.5-hr assay were lost by 2.5 hr. For some Tc-cell responses, only anti-H-2K antibodies have been found to be inhibitory, despite evidence of the expression of both H-2K and H-2D molecules on these cells. Some Tc-cell populations can be blocked by antibodies specific for both the H-2K and H-2D molecules. B10.A(4R) anti-Sendai Tc cells can be inhibited by anti-H-2Kk antibodies, but five different anti-H-2Db antibodies have been ineffective inhibitors. In contrast, B10.A(4R) anti-ectromelia Tc cells can be inhibited very effectively by each of these anti-H-2Db antibodies, as well as by anti-H-2Kk antibodies. Anti-H-2 antibodies also inhibit the function of cloned alloreactive Tc-cell lines such that the inhibitory capacity of antibodies specific for K versus D determinants appears to be consistent and specific for each Tc-cell line. A long-term Tc-cell clone, AR1, has been inhibited specifically by anti-H-2Kb and not anti-H-2Db antibodies, suggesting a clonally 'restricted' phenomenon.     

Major Histocompatibility Antigens on Trophoblast and Their Regulation: Implications in the Maternal-Fetal Relationship

ABSTRACT: Recent technological advances have provided methods of detecting antigens encoded by the major histocompatibility complex with greater precision, allowing the expression of such antigens on the components of the placenta to be clarified. Of specific interest is the expression of these antigens on trophoblast cells, the fetal-derived epithelial cells that confront maternal blood and tissues at the maternal-fetal interface. It is now clear that the different trophoblast subpopulations differentially express class I antigens, although none appear to express class II antigens. Class I antigens can be induced by exposure to interferons on some populations but apparently not others, suggesting that the regulation of their expression differs for sub-populations of trophoblast cells, depending on gestational stage and location. This restricted expression has important implications for maternal-fetal immune interactions during the different phases of pregnancy and perhaps also bears on physiological functions of the feto-placental unit, such as growth and differentiation.     

环孢霉素A对小鼠妊娠失败模型妊娠预后的影响

目的 :探讨环孢霉素A(CyclosporinA ,CsA)对小鼠妊娠失败模型及正常妊娠模型妊娠预后的影响。方法 :于孕 4d分别给小鼠妊娠失败模型及正常妊娠模型腹腔注射不同剂量 (0 ,5 ,10 ,15mg kg)CsA ,于孕 14d处死各组小鼠 ,观察各实验组胚胎吸收率、胎鼠及胎盘重量变化。结果 :①CsA可使小鼠妊娠失败模型胚胎吸收率显著降低 ,接近于小鼠正常模型胚胎吸收率 ;同时胎鼠及胎盘重量无显著性差异 ,但有增加趋势。②CsA对小鼠正常妊娠模型胚胎吸收率无明显影响 ;胎鼠及胎盘重量亦无显著性差异。结论 :于孕早期 (胚胎着床期 )腹腔注射CsA可使小鼠妊娠失败模型胚胎吸收率恢复至正常水平 ,从而可能成为保胎的潜在药物。     

Ontogeny of Expression of Pa and RT1.Aa Antigens on Rat Placenta and on Fetal Tissues

ABSTRACT: The unique pregnancy-associated (Pa) antigen, which is a class I antigen encoded by the major histocompatibility complex (MHC), elicits a nondestructive maternal antibody response. By contrast, the class I transplantation antigen RTI.A^a elicits a destructive antibody response in tissue transplantation but not during pregnancy. With the use of the avidin-biotin complex (ABC) immunohistochemical method, the Pa and RTl.A^a antigens were localized on the basophilic and giant cells of the basal zone trophoblast, the endovascular trophoblast and decidual interstitial trophoblast, and the chorioallantoic membrane but not on the labyrinthine zone trophoblast as early as the 12th day of gestation. These two antigens were also expressed on the epidermis, hair follicles, spleen, thymic medulla, bronchial epithelium, intestinal epithelium, the hepatic Kupffer cells, endocardium, endothelium of blood vessels, renal tubular cells and glomeruli, and renal pelvis and ureter of fetal and adult rat tissues. Absorption studies with placental tissue confirmed the presence of these two antigens in the rat placenta, and antibody-blocking studies confirmed their unique specificities.