Immunochemical Studies of Human Serum Gamma

The establishment of the quantitative precipitin reaction as an analytical-chemical procedure by Heidelberger and Kendall (1) was followed in 1937 by Kendall's original use of the method in the estimation of human serum proteins in health and disease (2, 3). A major drawback to the use of this immunochemical method for obtaining meaningful human serum protein values has concerned the purity or homogeneity of the specific protein used as the antigen (4). In particular, the heterogeneity of the human gamma globulin fraction, as defined electrophoretically, has been pointed out (5). Cohn, Deutsch and Wetter have demonstrated distinctive immunochemical behavior in various subfractions of the human serum gamma globulins (6). In these studies, however, the principal differences in immunochemical behavior of the subfractions were noted in zones of antigen excess; this zone is not employed in the studies reported herein. Although numerous physical, chemical and immunological criteria have been set forth for the establishment of protein purity, the lack of information regarding protein structure does not permit a clear definition of a single human protein species. In general, the proteins comprising the human serum gamma globulins separated by ethanol fractionation have an isoelectric distribution of pH 5.7 to 7.5; their electrophoretic mobilities range from 0.97 to 2.64. The marked antigenic similarity, indeed almost antigenic identity, of the members of this family of proteins in