Kinetics and mechanisms of macrophage activation by Corynebacterium anaerobium

Kinetics and mechanisms of macrophage activation by heat-killed Corynebacterium anaerobium (CA) in mice were investigated. The carbon clearance test revealed that the function of the reticuloendothelial system rose markedly on the 4th day after a single intravenous injection of CA and continued in a highly enhanced state until the 14th day. This activity declined gradually and dropped to a normal level around the 21st day. On the other hand, both lysosomal enzymes, beta-glucuronidase and acic phosphatase, of peritoneal macrophages decreased after the CA injection and then recovered, taking an almost inverse course to the function of the reticuloendothelial system. These results might be attributable to possible extracellular secretion of the lysosomal enzymes in accordance with macrophage activation by CA. A remarkable cytotoxicity of peritoneal macrophages, examined in vitro against L 929 cells, was detected on the 4th day following intraperitoneal administration of CA. It was maintained up to the 14th day and then declined rapidly. The mechanisms of macrophage activation by CA were also examined in vitro. CA-homogenate, heat-killed CA disrupted with an ultrasonicator, directly activated thioglycollate-induced macrophages. The macrophages were aslo activated by simultaneous treatment with both CA-homogenate and CA-sensitized spleen cells. Furthermore, the supernatant obtained from the culture of CA-sensitized spleen cells with CA-homogenate was capable of inducing activation of the macrophages. Conversely, the culture supernatant of spleen cells from CA-immunized athymic nude mice with CA-homogenate was unable to activate them. It was ascertained from the above-mentioned results that macrophages are activated initially by direct action of CA in a nonspecific way and subsequently by a soluble factor elaborated by CA-sensitized lymphocytes in an immunological way.