The antigenicity of human placenta

Studies of the normal human placental syncytiotrophoblast membrane: a combined immunological and physiochemical approach

In view of the importance of the syncytiotrophoblast in the immunobiology of human pregnancy, the composition of this interface between fetus and mother was further studied by a combination of physicochemical and immunological approaches. Trophoblast membranes were solubilized using three classes of detergents: zwitterionic (sulfobetaine14), non-ionic (Triton X-100), and anionic (deoxycholate). Quantitative studies of protein released demonstrated the importance of dispersion of membranes into detergent, and optimum solubilization was then obtained at detergent:protein ratios of 1.3:1 for sulfobetaine, 2.5:1 for Triton X-100, and 4.4:1 for deoxycholate. Analysis of chaotrope-treated detergent-solubilized membrane components was performed by preparative isoelectric focusing followed by combined physiocochemical and immunological methods. The results revealed three major proteins which were identified as placental alkaline phosphatase, albumin, and transferrin. Certain additional low molecular weight proteins were also evident; one of these components displayed physicochemical properties similar to those of actin, but none appeared to be recognized by conventional heteroantisera raised to trophoblast membrane. These findings and the results of further immunological analysis by affinity chromatography are consistent with the concept that human trophoblast may express limited immunogenicity due in part to the presence of large amounts of absorbed maternal serum components and limited expression of fetal proteins.

Immunoglobulin deposition in the kidney in pre-eclampsia: its significance

Renal biopsies from two patients with classical toxaemia of pregnancy demonstrated heavy deposition of IgG and IgA in a predominantly finely granular pattern. It is suggested that this may be a manifestation of immune complex formation and may provide further evidence for an immunological basis for the renal lesion of this poorly understood disease process.

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.

Twins, immuno-incompatibility and pre-eclampsia

A survey of 417 twin pregnancies is reported. Examination of the data revealed no difference in the incidence of pre-eclampsia referable to the zygosity of the twins. The findings thus lends no support to the hypothesis that immuno-incompatibility contributes to the aetiology of pre-eclampsia.

Immunologic aspects of term pregnancy toxemia. A study of immunoglobins and complement

IgA, IgG, and IgM were measured by the single radial immunodiffusion method in umbilical cord and maternal sera in toxemia patients and in normal term pregnant cases. Complement (C' 3) levels were determined only in maternal sera. Quantitation of IgA, IgG, and IgM was performed in concentrated serial urine samples from three eclamptic and three normal control patients. Results show that there are lower IgG and IgM levels in the sera of mothers with toxemia of pregnancy; however, paradoxically higher IgM levels were detected in cord sera from their newborn infants without evidence of placental leakage or increased neonatal infection. The finding of the low IgG and IgM levels appears to be due in part to immunoglobin loss into the urine. The unchanged complement levels in toxemia, in this study, are not suggestive of an active immunologic process, but the high IgM in the newborn infants of toxemic mothers is unexplained and may represent active immunologic disease. Clearly, investigations of tissue binding and the formation of immunoglobin complexes should be carried out to better explain these abnormal findings.

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.

Sex ratio of newborns: preponderance of males in toxemia of pregnancy

The ratio of males to females in 1061 babies born to mothers with toxemia of pregnancy is 1.24. The ratio increases as the severity of the disease increases, being 1.71 in cases in which the urinary output of protein is equal to or greater than 3 grams per 24 hours. Histoincompatibility of the fetus and mother, including incompatibility due to an antigen (or antigens) dependent on the Y chromosome, is suggested to function in the pathogenesis of pregnancy toxemia.