Vaccination against spontaneous abortion in mice by preimmunization with an anti-idiotypic antibody

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.

Immunological analogy between allograft rejection, recurrent abortion and pre-eclampsia - the same basic mechanism?

There are still controversies concerning the role of immunological mechanisms engaged both in recurrent abortions (RA) and pre-eclampsia (PE). According to some opinions, recurrent miscarriage is comparable to organ-specific autoimmune disease. Analysis of immune reactions shows that graft rejection shares many similar mechanisms with RA and PE. This fact allows us to conclude that rejection of transplanted alloantigenic organs and pregnancy loss have probably the same evolutionary origin. Subsets and functions of immunocompetent cells (T CD4, suppressor gammadeltaT, cytotoxic T CD8, Treg, Tr1, uterine NK cells), over-activation of innate immunity (activation of NK cytotoxic cells, macrophages, neutrophils and complement), changes of Th1/Th2 cytokine balance (IL-2, IL-12, IL-15, IL-18, IFNgamma, TNFalpha vs. IL-4, IL-10, TGFbeta), importance of HLA-G molecule, CD200/CD200R interaction, over-expression of adhesion molecules, fgl2 prothrombinase activation and stimulation of IDO and HO expression, all suggest that RA and PE are syndromes of fetal allograft rejection, and not organ-specific autoimmune diseases. According to that supposition, an analogy might exist between acute graft rejection and recurrent abortion, and between chronic graft rejection and pre-eclampsia.

An update in recurrent spontaneous abortion

Recurrent spontaneous abortion (RSA) is defined as three or more consecutive pregnancy losses prior to the 20th week of gestation. The etiology of recurrent spontaneous abortion is often unclear and may be multifactorial, with much controversy regarding diagnosis and treatment. Reasonably accepted etiologic causes include, genetics, anatomical, endocrine, placental anomalies, hormonal problems, infection, smoking and alcohol consumption, exposure to environmental factors, psychological trauma and stressful life event, certain coagulation and immunoregulatory protein defects. Detection of an abnormality in any of these areas may result into specific therapeutic measures, with varying degrees of success. However, the majority of cases of RSA remains unexplained and is found to be associated with certain autoimmune (APA, ANA, ACA, ATA, AECA) and alloimmune (APCA, Ab2, MLR-Bf) antibodies that may play major role in the immunologic failure of pregnancy and may lead to abortion. Alteration in the expression of HLA-G molecules, T-helper-1 (Th-1) pattern of cytokines and natural killer (NK) cells activity may also induce abortion. Various forms of treatment like antithrombotic therapies such as aspirin and heparin, intravenous immunoglobulin (IVIg) therapy, immunotherapy with paternal lymphocytes and vitamin D3 therapy are effective mode of treatment for unexplained cause of fetal loss in women with RSA.

From the decidual cell internet: trophoblast-recognizing T cells

The mammalian fetus has been perceived, paradoxically, as a successful allograft, a successful tumor, and a successful parasite. Success depends on fetal trophoblast cells, which form the interface with the mother. The maternal immune system is involved in the success of pregnancy and in its failure. The discovery that maternal gammadelta T cells may recognize and react to the fetal trophoblast and the definition of a vascular mechanism whereby their Th1 and Th2/3-type cytokines may abort embryos replaces confusion and debate with a new and simple clarity that enables further research.

A new method for isolation of human antisperm antibodies

A study was undertaken to isolate pure human antisperm antibodies from the sera of infertile couples. One hundred infertile couples attending the Infertility and IVF Unit (Beilinson Medical Center) because of unexplained infertility were tested (both partners) for antisperm antibodies. Sixty-eight experiments were performed with positive sera containing antisperm antibodies and normal donor sperm. These experiments were followed by experiments in order to elute pure human antisperm antibodies from the sperm surface. Three experiments were performed with human sperm which were found to be coated by antisperm antibodies, in order to directly elute these antibodies from the sperm surface. In all experiments we eluted antisperm antibodies of the IgG and IgA isotypes from the sperm surface. These antibodies were demonstrated in the eluate, in each case by either the indirect immunobead test, the radial immune diffusion assay, or the electrophoresis method. Control experiments were performed as follows: (i) normal donor sperm incubated with normal serum; (ii) normal donor sperm without serum incubation; (iii) normal donor lymphocytes incubated with serum containing antisperm antibodies; (iv) normal donor lymphocytes without serum incubation. No antisperm antibodies were obtained in any of these control experiments. Absorption and elution experiments can be used for the isolation of pure human antisperm antibodies, which may then be used for the production of anti-idiotypic antibodies to antisperm antibodies. The anti-idiotypic antibodies could be further utilized as antigen substitutes for the production of a contraceptive vaccine and/or for application in the treatment of spontaneous abortion and infertility.

Alloantibody responses to antigens recognized by rabbit antitrophoblast antisera in trophoblast and mononuclear cell (MNC) membranes by primary aborting women before and after paternal leukocyte immunization

PROBLEM

Because shared allogeneic antigens are expressed on peripheral blood lymphocytes, as well as trophoblasts, it has been proposed that lymphocyte transfusions may appropriately sensitize recurrent spontaneous aborters (RSA) to trophoblast and lead to pregnancy conservation. The degree to which these responses are affected by this treatment, however, has not been defined.

METHOD

SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analyses were used to study the alloantibody responses in RSA patients both before and after immunization with paternal leukocytes (MNC) against membrane proteins isolated from peripheral blood mononuclear cells (MNC), first trimester and full term chorionic villi (CV).

RESULTS

A distinct set of antigens with apparent molecular weights of 32, 36, 41, 63, 65, and 85 kDa was identified in both MNC and trophoblast membranes by rabbit anti-trophoblast antisera. In addition, a 55 kDa protein was recognized by MNC membranes. Thirty-eight percent of primary RSA sera recognized this 55 kDa protein. After paternal MNC immunization, all primary RSA samples displayed increased reactivity or produced antibodies to this 55 kDa protein when compared with preimmunization sera. The protein was identified as MCP using a rabbit polyclonal anti-MCP antisera. In contrast, reactivity to the other antigens present in the membrane preparations decreased after paternal MNC immunization.

CONCLUSION

Changes in immune reactivity in RSA patients after paternal MNC immunization suggest that immunization alters serum immune reactivity to MNC and trophoblast shared antigens.

The role of immunization treatment in preventing recurrent abortion

Published reports of controlled studies of immunization treatment in recurrent abortion have not shown any ability of either third-party cells or the husband's cells to prevent further abortions, whereas preliminary results of ongoing studies speak in favor of a beneficial effect of third-party cells. However, the lack of significant differences so far does not prove that immunotherapy in habitual abortion is ineffective, because all of these studies include too few patients in each group to give any conclusive results. Only a mega-trial could evaluate the efficacy and side effects of leukocyte immunotherapy. Such controlled studies are needed to clarify the true benefits, risks, and limitations of immunization treatment in recurrent abortion. Factors such as appropriate inclusion criteria, the time relationship between immunization and the next pregnancy, the number of immunizations required, the cell source and cell doses need to be established. Until this additional information is available this treatment should not be considered routinely indicated. This approach should be restricted to a few centers in order to provide maximal possibilities for collection and evaluation of the data.

Anti-idiotypic IgM antibodies to anti-HLA class I antibodies in habitual abortion

In order to investigate the role of the idiotypic network in miscarriages, sera from 28 habitually aborting women undergoing paternal leukocyte immunization were studied for the presence of HLA antibodies and related anti-idiotypes. Sixty-eight percent of sera from preimmunized patients which did not contain anti-lymphocyte antibodies inhibited the activity of antibodies to the HLA class I antigens expressed by the spouse. This inhibitory activity could be assigned to IgM antibodies, which cross-inhibit antibodies of similar specificity. This suggests that they are anti-idiotypes for the binding site of HLA antibodies. Immune sera of successfully treated patients exhibited both cytotoxic IgG anti-HLA antibodies and inhibitory IgM anti-idiotypic antibodies. A possible role for an intact idiotypic network in maintaining pregnancy is suggested.

Trophoblast immunity in human pregnancy defined by antiidiotype

Successful reproduction in mammals requires the mother to immunologically accept genetically disparate tissues. Allotypic trophoblast antigens (TLX) are thought to be responsible for influencing maternal acceptance of the feto-placental graft, and faulty regulation of immunity to TLX antigens has been associated with recurrent pregnancy losses. In this report, rabbit antiidiotype (RAb2) was produced to a human TLX antibody (Ab1). This RAb2 detected TLX cross-reactive idiotypes (CRI) on antitrophoblast IgG from women with normal and abnormal pregnancies. These findings support an hypothesis that women respond immunologically to allotypic trophoblast antigens, and that idiotype-antiidiotype regulation of this response is characteristic of normal pregnancy.