Decidua-associated antigens in the baboon.

Abstract

Proteins associated with the uterine decidua (DE) may control critical events in pregnancy. This study was undertaken, therefore, to study DE-associated antigens in the baboon. Three antigens, designated 1, 2, and 3, were detected in the cytosols of all 17 specimens of the baboon DE by Ouchterlony’s immunodiffusion test (ID), using an antiserum against a glycoprotein fraction of baboon DE. Antigens 1 and 2 were also found in one sample of the cytosol of the term placenta and in cytosols of all 30 endometria from cycling baboons, but not in any of the 30 samples analyzed of sera from nonpregnant baboons. Only antigen 2 was detected in all 17 samples of sera from pregnant baboons. Antigen 3 was detected only in DE cytosols but not in any of the cytosols of 30 endometria from cycling animals, 30 sera from pregnant animals, or one sample of term placenta. In addition to the three antigens mentioned above, the baboon DE was found to contain a protein which was immunologically similar, but not identical, to the progestagen-dependent endometrial protein or PEP which we have previously identified in women. The PEP-like material was found in cytosols of 11 of the 17 specimens of DE and of one term placenta, and in one sample of amniotic fluid. However, it could not be detected in any of the cytosols of th 30 endometria from cycling baboons, 30 sera from nonpregnant or 17 sera from pregnant baboons. These observations strongly suggest that the development of baboon endometrium during pregnancy is associated with the increase in tissue concentration of at least two antigenic proteins, namely antigen 3 and a PEP-like component.