Suppression of antibody formation by the res-blockade. Ⅲ. Effects of the res-blockade with methyl palmitate

The rats which received the repeated intra peritoneal or intravenous　injections of methyl palmitate showed a marked depressed phagocytic activity　of the RES as shown by the clearance test with radioactive iron as　well as by histological observations and a significantly suppressed antibody　formation against the challenge by BSA.　Differing from the cases of the blockade of the RES made by PVP or　radiogold, the injection of methyl palmitate did not result in any injurious　effect on the lymph follicles of lymph nodes and spleen and the plasma　cells proliferation as revealed by the histological observation. Histochemical observations of iron phagocytosis of the RES done by　Perls stain revealed that methyl palmitate　suppressed the phagocytic activity　of the Kupffer cells of the liver dramatically and also suppressed the　phagocytic activity of the sinus-lining cells in spleen to a lesser degree.　The result indicates that the injection of methyl palmitate attacks the phagocytic　function of the RES selectively and induces the reduced immune　response of the organism without giving any damages to the proliferation of immunologically com petent cells.　The fact suggests that the RES lowered in their phagocytic activity　fails to produce the informational substance for immune　response, showing　a lower level in the antibody formation even in the presence of antigen　and proliferating immunologically competent cells.