Immunological studies of phytohaemagglutinin. I. Reaction between phytohaemagglutinin and normal sera.

Studies of the precipitation of normal human serum by the kidney bean phytohaemagglutinin, (PHA), showed that the main serum components involved were α-macroglobulin, β-lipoproteins and γM immunoglobulins. Preparations of α-glycoprotein, orosomucoid and some γA immunoglobulins were also precipitated by PHA. Antisera prepared against the PHA—NHS precipitate recognized α-macroglobulin, β-lipoproteins and γM immunoglobulins, γG immunoglobulins and at least four other unidentified antigens in the β and α regions. PHA did not react with B or A, O blood group substances. Concanavalin A, a jack bean agglutinin, precipitated the same proteins which were precipitated by PHA but a extract did not react with human serum. Incomplete chemical studies of this interaction suggested that even though the same serum proteins were precipitated by Concanavalin A and PHA, the sugar specificity, if involved, is different for both lectins. Incomplete studies of the component or components of PHA involved in the PHA—NHS interaction suggested that three cathodally migrating proteins were recognized by both the antisera to PHA and to the precipitate formed by PHA and normal human serum.