Macrophages are required for the dextran-sulfate induced activation of B lymphocytes.

The proliferative response induced by the B cell activating ligand dextran-sulfate (DxS) requires the presence of macrophage-produced factors or the macrophage-substituting compound 2-mercaptoethanol. Thus, the mechanism for activation of mouse B splenic lymphocytes is different for DxS than for other polyclonal B cell activators such as lipopolysaccharides, which can trigger B cells directely in the absence of the helper factors. It is suggested that the disappearance of the DxS-induced response could be studied in a simple functional tests for the efficiency of macrophage depletion obtained by different techniques.