A SYNERGISTIC POLYCLONAL RESPONSE TO DEXTRAN SULFATE AND LIPOPOLYSACCHARIDE - IMMUNOGLOBULIN SECRETION AND CELL REQUIREMENTS

The effects of the simultaneous addition of lipopolysaccharide (LPS) and dextran sulfate (DxS) were studied in a low-cell density culture system, which enables extensive mouse cell proliferation and high Ig secretion. Using these 2 mitogens, a synergistic response was observed with regard to both cell division and IgM secretion. Only a very low IgG production could be detected. This was caused by the extensive cell proliferation, leading to suboptimal culture conditions. When the blasts were recultured at a lower cell density or when a lower initial cell concentration was used, a high IgG response was obtained. The synergistic response induced by LPS plus DxS was independent of T cells. No apparent need for phagocytic cells was found. Both the LPS- and the LPS plus DxS-induced activation led to a switch, preferentially to IgG2b and IgG3 secretion. This subclass pattern was not changed when the cultures were lacking functional T cells.