Antigenic Difference between Serum Amyloid Protein SAA and its Low Molecular Weight Derivative SAAL Revealed by an Anti-Amyloid A Antiserum at Different Temperatures1

Serum amyloid protein SAA and its low molecular weight derivative SAAL have been compared in immunodiffusion with an antiserum to amyloid A at different temperatures. At room temperature or at 37°C SAAL and SAA did precipitate with anti-AA forming a line of identity. At 4°C, however, only SAAL did react with anti AA. Experiments are described which show that the SAA-derivative SAAL has AA-related antigenic determinants exposed whereas these determinants are hidden in the parent SAA and are only exhibited as result of an unknown temperature-dependent process. Therefore, SAAL can also be distinguished from SAA by the availability of AA -related antigenic determinants for anti-AA antibodies at 4°C.