Immunosuppression in BALB/c mice bearing the plasmacytoma TEPC-183: massive increase in red pulp macrophages induced by the tumour.

An increase was found in total macrophage numbers in the spleens of BALB/c mice bearing the plasmacytoma TEPC-183 compared with controls. The increase was shown to be confined to red pulp macrophage; white pulp macrophage numbers were normal as were the number of macrophages which took up hydroxyethyl starch. It is suggested that this increase in red pulp macrophages may account for the suppression of primary immune responses caused by spleen cells from TEPC-183 bearing mice. This effect may be due to increased numbers of normal macrophages rather than the generation of distinctive suppressor macrophages as suggested previously.