Immunologic Differences Between the 19 S and 7 S Components of Normal Human γ-Globulin

Summary 1.The presence in normal human γ-globulin of molecules with an S 20,w = 19 S in addition to those with an S 20,w = 7 S is again demonstrated. 2.Antigenic differences between these molecules are shown by agar diffusion studies. 3.Quantitative precipitin studies confirm these differences and demonstrate that the “7” and “19” components partially cross react and are antigenically related. 4.The possibility is raised that the larger molecules are polymers of a smaller unit similar to 7 S γ-globulin but richer in carbohydrate and that antigenic differences may be due to the higher carbohydrate content as well as differences in size and shape.