The effect of BCG on extravascular mononuclear cell accumulation in vivo

BCG injection produces an increased accumulation of adoptively transferred 51Cr-labelled mononuclear cells at the site of inflammatory reactions in rats by two mechanisms. Systemic immunization induced a population of "activated" cells which, compared with controls, had an increased life span in the circulation after transfer and migrated in increased numbers to a chemotactic stimulus. These cells also were found in significantly greater than normal levels in the liver. In addition, local injection of BCG selectively attracted adoptively transferred mononuclear cells. These mechanisms help to explain local mononuclear cell accumulation which accompanies tumor rejection following intralesional or systemic BCG immunization.