Biphasic pattern of activation of the reticuloendothelial system by anaerobic coryneforms in mice.

Macrophage activation as measured by increased rates of clearance of carbon was explored in five inbred and two outbred strains of mice pretreated with anaerobic coryneform bacilli. Constant differences were found according to strain from DBA (lowest response) to Sha-Sha (highest response). The investigation was continued with mice of CBA strain which also provided highly reproducible and high-level responses. In this strain activation occurred in two phases: an early activation which reached maximum levels at 2 days and attributable to a lipid component of the bacteria, and a late phase reaching maximum at 14 days which appeared to coincide with greatly increased weight of the liver and spleen, due to infiltration by mononuclear cells. Evidence is provided that the early phase of macrophage activation is due to a lipid extract from the anaerobic coryneforms with chemotactic activity.