THE CARBOHYDRATE OF γ-GLOBULIN AND MYELOMA PROTEINS

Various preparations of γ-globulin homogeneous in the ultracentrifuge showed a similar content of hexose, hexosamine, fucose, and sialic acid. Subfractionation of Fr. II γ-globulin by zone electrophoresis revealed multiple components of different mean mobilities but containing similar amounts of carbohydrate. Gamma globulin isolated directly from normal serum by zone electrophoresis showed a heavy component in addition to the usual 7 S material. The heavy component (s (20, w) = 19 S) concentrated by preparative ultracentrifugation was found to be considerably richer in carbohydrate than the rest of the γ-globulin and accounted for small differences in carbohydrate content between different preparations of γ-globulin. Pathological sera with marked elevation in γ-globulin showed a carbohydrate-protein ratio for the γ-globulin similar to that found for the corresponding 7 S fraction in normal serum. This was only partially true of the myeloma proteins with a mobility in the γ-globulin region. Certain of these proteins showed slight but significant differences. The myeloma proteins of faster mobility (β-myelomas) contained considerably more carbohydrate. The possible role of these carbohydrates in accounting for some of the mobility and immunological differences in the myeloma proteins is discussed. The pathological proteins found in two cases of macroglobulinemia showed a high carbohydrate content similar to but slightly lower than the normal 19 S component of γ-globulin.