Abstract
The composition of serum seromucoid, the protein fraction of serum not precipitated by 0·6 M perchloric acid, has been shown to vary with the technique of preparation. Immunochemical examination revealed that 91·5% of the protein present in the seromucoid fraction of serum was α1 acid glycoprotein, the remainder consisting of α1 antitrypsin, α1 antichymotrypsin, β2 glycoprotein, haemopexin, albumin, and pre-albumin. Serum α1 acid glycoprotein concentration determined by radial immunodiffusion correlated well with serum seromucoid concentration although the former was usually 0·4 g/l lower. The determination of serum α1 acid glycoprotein by an immunological method is more precise than the seromucoid method and is not subject to interference from other proteins.