On a quantitative determination of antibodies to lipids and proteins.

The amount of precipitating antibodies in monospecific lipid- and protein antisera was determined by quantitative precipitation reactions according to the methods of Heidelberger and Kendall. Antisera were obtained by immunization of rabbits. Fragments of the thylakoid membrane from Antirrhinum chloroplasts were used as antigens for the binding of antibodies. These fragments had a diameter of 100 A. They were composed of 51% proteins and 39% lipids. It was found that antisera to the lipids mono-, tri- and digalactosyl diglyceride, sulfoquinovosyl diglyceride and phosphatidyl glycerol contained 20 to 92 micrograms precipitating antibodies per ml serum. In antisera to the coupling factor of photophosphorylation, cytochrome f, a polypeptide with the apparent MW 24000 and a serum to the total protein of the lamellar system 23 to 99 micrograms were found. In chloroplast antisera the amount of all precipitating lipid- and protein antibodies amounted to 765 micrograms per ml. The described antisera originated from blood that had been withdrawn from the test animals 4 to 10 week after antigen injection.