The serum myeloma proteins associated with 20 mouse plasma cell tumors in C3H or BALB/c mice that had proved transplantable were characterized by electrophoretic and immunochemical techniques. Although the myeloma proteins ranged in electrophoretic mobility from gamma to alpha globulins, they could be divided into two groups, the gamma type and the beta type myeloma globulins, on the basis of characteristic immunochemical properties. Gamma type myeloma proteins (5563, MPC-11) showed a close immunochemical relationship to normal mouse gamma globulins.
Eighteen beta type mouse myeloma proteins migrated as beta or alpha globulins on zone electrophoresis. These proteins shared common antigenic features which permitted their recognition, separate from gamma myeloma proteins. The beta type myeloma proteins were shown to be related to a beta globulin component present in normal serum. Strain differences were observed for the normal beta globulin component believed to be formed in plasma cells.
The proteins formed in mouse plasma cells were found to be antigenically complex. Shared antigenic determinants as well as distinctive antigenic determinants were detected when representative myeloma proteins were purified and compared by the Ouchterlony double diffusion technique.
The myeloma proteins associated with each of the transplantable plasma cell tumors in mice are regarded as distinctive and characteristic products of plasma cell metabolism. The variety of myeloma globulins was similar for plasma cell tumors arising in C3H as well as in BALB/c mice, indicating that differences in mouse strains would not account for the differences among the myeloma globulins. These differences, however, may be due to differences among the normal plasma cells from which the malignant cells are derived. If this is so, the variety of myeloma globulins reflect the variety of plasma cells present normally.