Studies on the cellular recognition mechanism: effect of concanavalina on the phagocytosis of homologous red cells by peritoneal macrophage

As the first step to analyze the autoimmune disease of red cells the recognition mechanism of macrophage to red cells or erythrophagocytosis has been studied in vitro by using mouse peritoneal macrophage and homologous and cells and the following results were obtained: 1. In Hanks solution, the mouse macrophage hardly phagocytizes living red cells, both homologous and heterologous ones. But in the presence of mouse serum, the macrophage phagocytizes heterologous red cells selectively but does not phagocytize homologous ones. 2. The macrophage actively phagocytized homologous red cells prior to treatment with concanavalin A (Con A) at a concentration as low as 1.95 ltg/ml. 3. Red cell agglutination was clearly recognized in those treated with Con A at 62.5 lag/ml or more, but not at 1.95 ltg/ml. 4. The red cell agglutination by Con A was inhibited with D-glucose, D.mannose and a-methyl glucopyranoside at the concentration as low 1.5 mM, while the phagocytosis was suppressed only at a very high concentration of the sugars, 1, 000 mM. 5. Fragility test of the red cells treated with Con A showed a lower resistance of red cells to hypotonic solution than those treated with Con A at the concentration of 31.25 p.g/ml or more 6. Electron microscope observation revealed no membrane damage of red cells by treating with Con A at a concentration of 1.95 ,ag/ml, where erythrophagocytosis was observed. The membrane damage occur. red by treating with Con A at 31.25 ltg/ml or higher. 7. All the data indicate that the phagocytosis of homologous red cells by macrophage is induced by the adherence of a small amount of Con A, which induces no detectable changes of red cell surface and red cell membrane as revealed by agglutination test, fragility test, electron microscope observation and circular dichroism. On the basis of these observations a possible recognition error to homologous red cells by adsorbing a minute quantity of foreign substances on their surfaces has been discussed.