Suppression of antibody sensitized tumor cells by macrophages: Insufficient supply or activation of macrophages within large tumors

Systemic administration of antibody against the C3H lymphosarcoma 6C3HED caused complete suppression of the growth of 10⁵ tumor cells. When the size of the tumor inoculum was increased to 10⁶ tumor cells, excess antibody was unable to cause complete suppression unless exogenous macrophages were added to the tumor inocula. The decreased effectiveness of antibody was shown to be caused by a local deficiency in the supply of activation of macrophages within the large tumor grafts and not by a systemic deficiency.