Immunochemical detection and characterization of pregnancy-associated endometrial 1- and 2-globulins secreted by human endometrium and decidua

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Abstract
Antisera raised against the soluble antigens of the endometrium of early pregnancy detected 2 antigenic proteins of .alpha.1 and .alpha.2 mobility in extracts of this tissue and were termed antigens A and B. Neither antigen was detected in pregnancy sera or extracts of proliferative endometrium, but antigen B was detected in extracts of secretory endometrium and both were present in amniotic fluid and medium from in-vitro incubations of pregnancy endometrium. Fractionation of radiolabeled medium on ion-exchange chromatography demonstrated that antigens A and B co-eluted with the proteins from which EP14 and EP15 were derived and which were the major secretory polypeptides of pregnancy endometrium in vitro. Further biochemical purificaton revealed that EP14 (MW 32,000) was derived from a protein of native MW 36,000 which existed in 2 forms, whereas EP15 (MW 28,000) was derived from a dimeric glycoprotein of native MW 56,000. Immunochemical studies demonstrated that antigens A and B are identical to these 2 secretory proteins and have been termed pregnancy-associated endometrial .alpha.1- and .alpha.2-globulins (.alpha.1- and .alpha.2-PEG).