Comparison of membrane IgM expression in the murine B cell lymphoma 70Z/3 treated with LPS or supernatant containing T cell factors.

The cultured murine B cell lymphoma, 70Z /3, can be induced to express membrane IgM ( mIgM ) after exposure to lipopolysaccharide (LPS) or T cell-derived factors. The kinetics and magnitude of the responses have been compared in wild type 70Z /3 cells and three variants by using flow cytometric analysis and immunoprecipitation. Wild type 70Z /3 cells respond to LPS more quickly and with twofold greater mIgM than to concanavalin A-induced spleen cell supernatant (CAS). Variants were selected for their abnormal mIgM expression in response to LPS, but individual variants also showed normal, aberrant, or no response to CAS. When cells were induced with suboptimal amounts of LPS and CAS, a synergistic effect on the magnitude of mIgM expression was seen in wild type and variant cells. This suggests that both inducing agents are utilizing some part of a common inductive mechanism. The different responses of the variant cell lines will allow further genetic dissection and comparison of the mIgM expression pathways used in response to LPS and CAS.