Abstract
Starch electrophoresis was used to separate allergic sera into electrophoretically distinct albumin, alpha-, beta-, and gamma-globulin fractions. The identity of the various fractions was established by free and paper electrophoresis. The gamma-globulin fractions were also characterized by ultracentrifugation. The serum skin-sensitizing antibody to ragweed pollen was shown to be associated with the gamma-globulins in fourteen allergic sera by means of passive transfer technique. The mobility of the skin-sensitizing antibody corresponded to that of gamma-1 and/or gamma-2 globulins. All the other serum fractions were devoid of reaginic activity. Reaginic activity per se was not directly related to protein concentration. The discrepancies between these results, and those obtained by others and ourselves previously are discussed.