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The relationship of Bence Jones protein (mol wt = 45,000) to a beta(2A)-myeloma protein (mol wt = 160,000) formed by the same mouse plasma cell tumor (MPC-2) was investigated. The beta(2A)-myeloma protein was split by treatment with papain and cysteine into fragments (S(20,w) = 3.7S), similar in size to the Bence Jones protein (S(20,w) = 3.6S). Two types of fragments with distinct antigenic groupings designated S and F, were present in the MPC-2 myeloma protein digest. These were partially separated by DEAE-cellulose chromatography. The Bence Jones protein was found to share antigenic determinants with S fragments from the MPC-2 beta(2A)-myeloma protein and with S fragments from gamma-globulins. Physicochemical observations indicated, however, that the Bence Jones protein was not identical to the globulin fragments produced by treatment with papain and cysteine. Comparison of the S and F fragments from beta(2A)- and gamma-globulins revealed that the antigenic features shared by the various globulins derived from plasma cells (gamma- and beta(2A)-myeloma proteins, the range of normal gamma-globulins) are largely properties of the S fragments, whereas the distinctive antigenic differences between the gamma- and beta(2A)-myeloma proteins were properties which appeared in the F fragments of the molecules.

Peritoneal macrophages were cultured for several hours after uptake of (131)I-hemocyanin. The cells degraded most of the (131)I-labeled protein within 2-5 hr. Their ability to prime lymphocytes of syngeneic mice for a secondary immune challenge remained unchanged for long periods of time despite the loss of more than 90% of the original content of antigen. The persistence of immunogenicity was associated with a small percentage of antigen retained by the cell in a form which was protected from rapid breakdown and elimination.

Gamma globulin and antibody obtained from inbred C(3)H mice are split by papain and cysteine into fragments roughly one-third the size of the original Molecule (S(20,w) = 3.5S). The papain digests were characterized by starch gel electrophoresis and immunological methods. The highly heterogeneous fragments could be divided into two groups with distinct antigenic determinants (S and F), which were separated by DEAE ion-exchange cellulose chromatography. Approximately two-thirds of the fragments had S antigenic groupings and one-third had F antigenic groupings. These data are consistent with the view that mouse gamma globulin is split by papain and cysteine into three major fragments, two of which are of the S type and one of the F type. Antibody activity of the original molecule was present in the S fragments. Although the S fragments did not precipitate the antigen (hemocyanin) they were shown to bind antigen specifically in the manner of univalent antibodies. The S fragments of normal gamma-globulin were very heterogeneous with a broad spectrum of electrophoretic mobilities. Comparison of S fragments from slow and fast migrating globulins showed that the mobilities of the original gamma-globulin samples were largely reflected in the mobilities of their S fragments. Additional observations indicated that the F fragments also may help to determine the electrophoretic mobility of intact gamma-globulin molecules. S fragments of differing electrophoretic mobility were shown to have the same antigenic determinants, indicating that the structural differences responsible for the electrophoretic mobility differences were not involved in the antigenic groupings identified with rabbit antisera. The F fragments of normal gamma-globulin migrated more rapidly than the S fragments, were less heterogeneous, and showed several bands on starch gel electrophoresis. The F fragments differed antigenically from the S fragments, and had no antibody activity. Two groups of F fragments (F and F') were detected with some antisera. The gamma-myeloma protein (5563) formed in a C(3)H plasma cell tumor and similarly fragmented by treatment with papain and cysteine, produced much more discrete S and F components than were found in the normal gamma-globulin digest. The electrophoretic properties of the myeloma protein fragments were within the range observed for normal gamma-globulin fragments. Although the gamma-myeloma protein shares antigenic determinants with normal gamma-globulins it lacks some of the antigenic groupings present in the gamma-globulin preparation. Both S and F fragments from the myeloma protein share antigenic determinants with the corresponding fragments from normal gamma-globulin. In addition, both S and F fragments of normal gamma-globulin possess antigenic groupings not present in fragments of the gamma-myeloma protein, accounting for the antigenic deficiency observed on comparison of the gamma-myeloma protein with normal gamma-globulins.