Two Types of 6.6 S γ-Globulins, β_2A-Globulins and 18 S γ₁-Macroglobulins in Normal Serum and γ-Microglobulins in Normal Urine¹ Free

Two types of γ-globulin antigenic determinants (I and II) are described. These determinants are common to all γ-globulin groups. The 6.6 S γ-globulins, γ₁-macroglobulins, and β_2A-globulins of normal serum, and the γ-microglobulins of normal urine were divided into two types by the presence of type I or II antigenic determinants. Individual γ-globulin molecules appear to have either type I or II, but not both, types of antigenic determinants.

All individual sera tested had both type I and II γ-globulin molecules. In normal serum the type I γ-globulins predominate in a ratio of about 2:1. Similar ratios were observed in normal serum 6.6 S γ-globulins and γ₁-macroglobulins, but more nearly equal ratios of type I and II molecules were found in the γ-microglobulins of normal urine.

Type I and II γ-globulin molecules are similarly distributed throghout the entire range of electrophoretic mobility of normal γ-globulin. Type I and II γ-globulin molecules also are similar in ultracentrifugal and chromatographic behavior and in hexose content. Preliminary observations, however, indicate that the InV genetic factors are more likely to be on type I than on type II molecules.