Immunochemical and biological studies on two molecular variants of pregnancy specific beta 1 glycoprotein (SP1) SP1 alpha and SP1 beta.

Analytical crossed immunoelectrophoresis was performed to examine the relationship of a high molecular mass alpha 2 mobile glycoprotein (SP1 alpha) which is immunochemically identifiable with pregnancy specific beta 1 glycoprotein (SP1 beta). There was no evidence for any reaction of SP1 alpha with antisera to normal human serum protein, nor for complex formation following incubation with normal serum proteins. The half-life of SP1 alpha was apparently shorter than that of SP1 beta after delivery of the placenta.