Antigenicity of mouse placental tissue

Detection of human and murine trophoblast-specific antigens and an assessment of their species specificity

The distribution and species specificity of human and mouse trophoblast-specific surface antigens detected by heterologous anti-mouse ectoplacental cone (anti-EPC) trophoblast and anti-human first-trimester trophoblast plasma membrane (anti-TrPM) antisera were assessed using several immunochemical and immunolabelling assays. The findings with immunofluorescence assays using anti-EPC antiserum on monolayer cultures indicate that the expression of mouse trophoblast-specific antigens is restricted to the major trophoblast components of the mouse placenta, as well as pre- and early post-implantation trophoblast, and does not occur on fetal, amnion or tumour tissues. The anti-EPC antiserum does not cross-react with human chorionic villous trophoblast. The human trophoblast-specific antigens also displayed species specificity. The anti-TrPM antiserum showed no evidence of cross-reactivity with rhesus monkey, rabbit, guinea pig or mouse trophoblast by immunodiffusion, crossed immunoelectrophoresis, immunofluorescence or immunoperoxidase labelling.

Cellular hyperreactivity to placenta in toxemia of pregnancy

It is generally assumed that maternal immune response may be involved in some pathological conditions of pregnancy, such as toxemia. The activity of cell-mediated immunity to placenta was studied in women with gestosis. The leucocyte inhibition technique was employed to test reactivity of peripheral blood leucocytes from postpartum women. The results indicated that leucocyte migration was significantly inhibited in the presence of placental microsomal fraction when blood from toxemic women was used. Thus, about 87% out of 30 studied cases of toxemia showed positive results. At the same time, in only 22% of women with uncomplicated pregnancy was such a positive leucocyte migration inhibition test found. There was no correlation between the severity of the toxemic symptoms and the extent of inhibition. In further experiments the leucocyte migration inhibition test with the microsomal fraction antigens from cadaver kidneys was performed; only 1 out of 6 patients showed positive leucocyte migration inhibition. These findings may suggest that the normal status of the mother is altered towards cellular hyperreactivity to placental antigens in toxemic pregnancy.

Placental lesions in habitually aborting cats

An ovariohysterectomy was done on five female cats with a history of habitual abortion in the 3rd to 4th week of pregnancy and the foetuses and placentas examined. Histologic and electron microscopic examination showed multifocal placental necrosis which was deduced to begin in the syncytial trophoblastic cells and to extend to all the cells of the labyrinth. This lesion was followed by foetal autolysis. No bacterial, viral or mycoplasmal agents could be incriminated in the disease.

A blocking factor in amniotic fluid causing leukocyte migration enhancement

Amniotic fluid was found to cause significant leukocyte migration enhancement during the second and third trimester of pregnancy and in the early postpartum period when compared to the migration area obtained with an ovarian tumor homogenate antigen (p less than 0.01), choriocarcinoma spent medium (p less than 0.01), and placental pool homogenate (p less than 0.01). Only borderline significance (p less than 0.1) was obtained when migration enhancement with AF was compared between pregnant and nonpregnant female control patients, indicating minimal unspecific activity of AF. Migration enhancement with autologous amniotic fluid was slightly larger than with homologous amniotic fluid, but the difference did not reach significance (p less than 0.4). None of the control antigens caused migration enhancement; placental pool homogenate in concentrations above 4 mg. per cent caused migration inhibition but did not in lower concentrations. The enhancing effect of AF could be abolished by dilution but not by addition of excessive antibody to estrogen of HCG. It is suggested that a blocking factor is present in AF preventing recognition of fetoplacental antigen by the maternal immune system. Thus in vitro leukocyte migration enhancement may correlate to in vivo graft enhancement.

Embryotoxic effects of heterologous antisera against rat Reichert's membrane

Parietal yolk-sacs of rat embryos at the fifteenth day of gestation were obtained by microdissection. A Reichert's membrane (RM) preparation was isolated by treating the parietal yolk-sacs with the chelating agent tetrasodium salt of ethylenediaminetetraacetic acid (EDTA) combined with mechanical shaking. Less than 1% of the membrane preparation was DNA and phosphorus contaminants. The membrane purity was also evaluated by electrom microscopic examination. Rabbit Ig G directed against the RM preparation when injected ip into ninth day pregnant rats produced malformations, fetal growth retardation and resorption. Fluorescent-labeled antibody localization studies demonstrated that the teratogenic antibodies localized in RM. It is postulated that RM antibodies induce teratogenesis by interfering with the function of RM.

Immunologic aspects of pre-eclampsia

It has been suggested by a number of investigators that immune reactions of the mother against antigens of her conceptus contribute to the development of pre-eclampsia. Evidence for and against this hypothesis is reviewed and the possible clinical implications are discussed.

Immunobiological function of the syncytiotrophoblast: a new theory

The main purpose of this paper is to present our hypothesis concerning the antigen-antibody complex formation and the resolution system inside the syncytiotrophoblast to explain immunologic fetomaternal relationships. This hypothesis, derived from the results of our experiments, might be an answer to why the fetus is not rejected by the mother, in contradistinction to other allografts. We also believe that this hypothesis makes important contributions to the explanation of the immunologic processes of cells, i.e., those processes which work against antigens inside a living body.

[Antigens of the human placenta (author's transl)]

The immunologic relations between mother, foetus and placenta are discussed and those antigens of the human placenta already characterized by their physico-chemical and immunochemical properties described. In diagnostics the detection and determination of placental proteins is used in pregnancy tests, for the evaluation of placental functions and the detection of malignant diseases. Antibodies to placental antigens have an abortive effect; immunization against placental specific proteins may have implications as an immunologic contraceptive method and for the immunotherapy of choriocarcinoma.

Further evidence concerning the autoantigenic status of the trophoblast

Heterologous antisera were raised by inoculation of rabbits with fairly pure suspensions of trophoblast, lymphoid, fetal (excluding placental components), epidermal, decidual, and renal cells from Fischer rats. After absorption of hemagglutinins, these antisera were assayed for abortifacient activity by intramuscular inoculation into time-mated Fischer females. The anti-trophoblast serum aborted all the recipients, but had some nonspecific activity in that it caused the deaths of 12% of them. Anti-lymphocyte serum was more toxic and less potent as an abortifacient. None of the other sera harmed either the mothers or their fetuses. However, the anti-kidney cell serum caused kidney lesions. Absorption of the anti-trophoblast serum with lymphoid cells completely removed its toxicity for the pregnant females without perceptible impairment of its abortifacient activity. However, the latter could be removed by absorption with trophoblast cells. (a) The lymphocyte-absorbed anti-trophoblast serum was equally effective in aborting rats over the range 7-18 days postconception; (b) a single injection of 1 ml was sufficient in most cases, and (c) it was equally efficacious in terminating gestation in rats irrespective of their genetic constitution, and (d) its effect was highly species-specific. These findings support the premise that a unique antigen (or antigens), of possible clinical significance, is associated with trophoblast cells.