Activation of reticuloendothelial system macrophages and enhancement of host resistance to a transplantable osteogenic sarcoma in mice by an extract of Brucella abortus.

An aqueous-ether extract of Brucella abortus, Bru-Pel, enhanced resistance of mice to a transplantable osteogenic sarcoma (OGS). The results presented in this report suggest that Bru-Pel is an effective immunomodulator and that one mechanism through which it enhances host resistance is activation of phagocytic cells of the reticuloendothelial system. Peritoneal macrophages from mice inoculated with Bru-Pel 14 days previously were cytotoxic for OGS cells in vitro, limited the multiplication of vaccinia virus in cell cultures, and demonstrated increased chemiluminescence during phagocytosis. Furthermore, Bru-Pel enhanced host resistance to Listeria monocytogenes, in addition to viral infections and a transplantable tumor. These results support the hypothesis that Bru-Pel shares a number of characteristics with other recognized immunomodulating agents and suggest that further studies are warranted to better define the potential of Bru-Pel for immunotherapeutic regimens in man.