VARIATIONS IN THE SERUM CONCENTRATION OF A HUMAN PREGNANCY-ASSOCIATED -MACROGLOBULIN DURING PREGNANCY AND AFTER DELIVERY

Abstract

An immunoassay technique was used in which serum samples were incubated in antibody-coated polystyrene tubes for 45 min at 37.degree. C. After washing with 10% Triton X-100 solution, and an antibody-horseradish peroxidase conjugate was added and the tubes were reincubated. The test-tubes were then washed and the peroxidase activity remaining bound was determined spectrophotometrically. This sandwich-type enzyme immunoassay had a limit of sensitivity of approximately 200 ng/ml and the results were highly reproducible. Throughout pregnancy and up to 11 wk post partum, there were considerable individual variations but PAM [pregnancy associated .alpha.-macroglobulin] levels normally rose sharply in the 1st trimester and fell rapidly after delivery. The level reached a plateau during the 3rd trimester and within 6 wk after delivery declined to a comparatively minimal concentration. All women sampled had uncomplicated pregnancies and gave birth to healthy children in spite of the great individual variations in PAM levels encountered. If the macromolecule does contribute to maternal immunological unresponsiveness, it apparently must act with other factors also capable of inducing suppression.