Characterization of macrophage functions in mice infected with Brucella abortus.

Macrophage spreading, surface receptor density/avidity, phagocytosis, random migration, chemotactic responsiveness, and serum lysozyme were examined during the course of infection (up to 60 days) of mice with Brucella abortus strain 19. Markedly enhanced in vitro spreading activity was observed throughout the period of study. The density/avidity of cell surface immunoglobulin G Fc receptors was increased for up to 60 days postinfection. Internalization of sheep erythrocytes via C3 receptors was significantly enhanced. Random locomotion and chemotactic responsiveness to lymphocyte-derived chemotactic factor and N-formyl-L-methionyl-L-leucyl-L-phenylalanine were markedly stimulated. Serum lysozyme was also elevated in infected animals. These changes indicated significant and prolonged enhancement of macrophage activity during Brucella infection. These findings are discussed in relation to previous reports describing macrophage activation by Brucella.