Immunological observations on the relationship of SP 1 alpha to SP 1 beta.

SP 1 alpha and SP 1 beta in pregnancy sera were separated by gel chromatography. When these proteins were subjected to crossed immunoelectrophoresis with an antiserum to non-pregnant human serum in the first dimension gel, SP 1 alpha was absorbed but SP 1 beta was unaffected. Similarly incubation with such an antiserum caused the precipitation of SP 1 alpha but not SP 1 beta. When SP 1 antiserum was absorbed with either SP 1 alpha or SP 1 beta it resulted in the removal of all antibodies to either SP 1 alpha or SP 1 beta.