Suppression of synthesis of immunoglobulin in mouse myeloma cells by alloantibody

Summary

Alloantibody-containing globulins that can suppress the production of hemolytic antibody plaques by antigenically stimulated Balb/c spleen cells were tested for their effect on Balb/c plasmacytoma cells. Two plasmacytomas, MOPC 21 and MOPC 315, which normally produce IgGl and IgA, respectively, were treated with CBA anti-Balb/c globulin from which the cytotoxic antibody had been largely removed by differential absorption. The effects on synthesis of the Ig's were studied in three experimental modes.

1. When the tumor cells were pretreated with the antibody before incubation with ³H-thymidine labeled aminoacids, there was suppression of the synthesis of immunoglobulins, as measured in both the cell contents and the medium. The suppression was most marked at the highest concentration of antibody and decreased progressively with dilution. In the case of other or smaller peptides not precipitated by anti-Ig but precipitable by TCA, this could be demonstrated only in the most recently synthesized peptides, those found within the cells.

2. When the exposure to the suppressive antibody was simultaneous with the incubation of tumor cells and labeled aminoacids suppression was again demonstrated, indicating that the suppressive effect was expressed as early as the synthesis of the peptides.

3. Even when the exposure to labeled aminoacids began before the incubation with antibody, the cell contents, which included the most recently synthesized peptides, still showed the same effects of the successive dilutions of the suppressive antibody as the cell contents from the other modes of exposure. In the medium, however, there was an additional effect under these experimental conditions. Labeled material appeared in amounts that increased with increasing concentration of the suppressive antibody, suggesting the release from the cells of the peptides whose synthesis was interrupted by the antibody.