Demonstration of an analogue to human pregnancy zone protein in the African green monkey.

A serum protein in the grivet (Cercopithecus aethiops), immunologically cross-reacting with human pregnancy zone protein (PZP), is found in males as well as in nonpregnant females. The electrophoretic mobility, antigenic cross-reactivity, molecular weight, and carbohydrate structure appear analogous to PZP; however, contrary to the situation in man, exogenous estrogens cause a fall in serum concentration of the protein.