Specific assay for pregnancy-specific-beta 1-glycoprotein (Sp1-beta).  Preparation of antiserum specific for SP1-beta by absorption with a crossreacting high molecular weight serum protein. 
Two pregnancy-associated proteins reacting with antibody against pregnancy-specific beta 1-glycoprotein (PS beta G or SP1) were separated by means of ammonium sulphate precipitation, size chromatography and preparative zone electrophoresis.  The antibody preparation was made monospecific to the beta-mobile protein by liquid phase cross-absorption of anti-SP1 immunoglobulin preparation with the isolated alpha2-mobile high molecular weight protein.  The specificity of the absorbed antibody was tested in line immunoelectrophoresis, rocket immunoelectrophoresis and crossed immunoelectrophoresis.