Use of heterophilic agglutinins in plant serology.

Abstract

In previous communications it has been demonstrated that monogalactosyl diglyceride and the anionic chloroplasts lipids can be detected on the thylakoid membrane by specific antisera 1 _ 3 . The antigen determinants are of carbohydrate nature as was shown by specific agglutination inhibition tests. They are located on the outer surface of the thylakoid membrane and are directly accessible to the antibodies. The latter has been proven for the monogalactolipid 1, whereas the determinants having the carbohydrate structure like that of sulphoquinovosyl diglyceride2 stick out of the surface like phosphatidyl glycerol too 3, but are topographically rather arranged in gaps or pores of the membrane. Fatty acids are not involved in this antigenantibody reactions as precipitation studies with hydrated lipids and with lipids of different fatty acid compositions have revealed. On the other side, if sugar components represent the immunologically determinant groups, then it should be possible to confirm the results obtained with vertebrate antisera by using heterophilic agglutinins from plants (so-called lectins) 4, invertebrates and fish eggs. These are known to be excellent tools for the specific detection of terminal and innerchain carbohydrate structures of different configurations and conformations 5. As D-galactose is the main determinant sugar in plant glycolipids, we tested some of the galactose specific lectins in our system. It could be found, that the agglutinin from Ricinus communis, the antigalactosyl specificity of which is well established4, agglutinated chloroplasts and thylakoidfragments in a very specific way. This agglutination was inhibited by 0.03 M D-galactose, 0.06 M lactose, raffinose, stachyose, monogalactosyl glycerol (/9-glycosidic linkage), and digalactosyl glycerol (a-glycosidic linkage of D-galactose), but not by D-glucose, and L-arabinose. In addition, the specific anti-a-galactosyl agglutinin6 ("anti-B") from Salmo trutta (trout) also reacts well, especially after protease treatment. It is inhibited by carbohydrates with terminal a-glycosidic bound D-galactose (raffinose, stachyose, digalactosyl glycerol 0.03 M) and not by monogalactosyl glycerol, lactose, D-glucose, Dand Larabinose. We got weaker reactions with agglutinins from fungal origin like Fomes fomentarius, a lectin known as anti-B (a-galactosyl) reagent4'7, whereas other agglutinins (Arachis hypogoea "anti-T") directed to D-galactose-like structures 8 gave very weak aggluti-