The immunochemical properties of proteins formed in plasma cells of inbred mice were studied by comparison of intact molecules and S and F (papain-produced) fragments of γ- and β2A-myeloma proteins from BALB/c and C3H/He mice.
Mouse β2A-myeloma proteins were reduced to two antigenically different classes of fragments (S and F). Each molecule appeared to contain two S and one F piece. The F fragments of the β2A-myeloma proteins could be crystallized.
Antigenic determinants specific for β2A-globulins were found on the F fragments. The antigenic determinants common to both the γ and β2A-globulins were found on the S fragments of both globulin types.
Two γ-myeloma proteins from BALB/c plasma cell tumors were found to have distinctive as well as common antigenic determinants. The antigenic differences were located in both the S and F fragments.