Central suppression of monoclonal B cells: DNP-MGG suppresses proliferation and immunoglobulin synthesis in anti-DNP-secreting hybridoma and myeloma

Our laboratory has established that 2,4-dinitrophenyl-conjugated mouse IgG (DNP-MGG) can specifically suppress the anti-DNP secretion in hybridoma 35-12 and plasmacytoma MOPC-315 cells. To further study the mechanism of this suppression, the effect of DNP-MGG on anti-DNP synthesis and cell proliferation was investigated in these cell lines. Cultured tumor cells (1 × 10⁶) were injected ip into syngeneic mice. These mice were then given either 1 mg MGG or 1 mg DNP-MGG. At different days after injection, tumor cells obtained from these mice were assayed for anti-DNP secretion, anti-DNP synthesis, cell proliferation, and tumor cell size. When the anti-DNP secretion was suppressed by DNP-MGG, the intracellular synthesis of anti-DNP, demonstrated by [³H]leucine incorporation into DNP-binding activity, was also suppressed. Simultaneous assays of [³H]thymidine incorporation demonstrated that proliferation was also suppressed. Tumor cells injected ip into mice normally become small nonsecreting cells and later return to preinjection size and secrete antibody. Those cells whose antibody synthesis and proliferation were suppressed by DNP-MGG remained smaller.