A two-dimensional electrophoretic study of serum amyloid A and C-reactive protein in infants and children.

Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) was used to analyze C-reactive - (CRP) and serum amyloid A protein (SAA) in infants and children. Five SAA isotypes were identified. CRP showed vertical streaking, and its optical density values correlated with immunoturbidimetric measurements. As evaluated by densitometry, both proteins showed an age-dependent variation. In more than 50% of the neonates, SAA was present in equal or higher amounts than CRP, and only SAA1alpha could be detected. In children, CRP was expressed in higher amounts than SAA, and both SAA1alpha and SAA2alpha were present. N-terminally modified forms of both isotypes were present regardless of age, including in premature infants. These results suggest that the overall synthesis of the gene products SAA1alpha and SAA2alpha is developmentally regulated, but at the same time that their N-terminal processing occurs independently of developmental factors. The presented data suggest that SAA has an important function in neonates, and that the role of SAA as an infection marker in this population should be investigated further.