Characterization of macrophage functions in mice infected with Brucella abortus

Abstract

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.

Immune serum-mediated effects on brucellosis evolution in mice

“…Vet., in press). This precludes any clear conclusion, which may be made more difficult by the following facts: PG and LPS are both polyclonal activators (23,24,40), which may modify the type and avidity of immunoglobulins elicited; PG and LPS used as vaccines in mice interact negatively on immunity (5); in murine brucellosis, macrophages do have an elevated general activity with, in particular, an enhanced immunoglobulin G Fc receptor activi-ty, which may facilitate attachment and lysis of bacteria (4). However, before research in progress using purer fractions, antibody titrations of each immunoglobulin class, and complement is completed, it is clear from the use of polysaccharide cross-reacting bacterial antisera that polysaccharide antibodies were involved in lymph node barrier and transfer (early) effects, but that only PG (and infected) sera exhibited a total barrier and a regularly strong late effect.…”

Brucella requires a functional Type IV secretion system to elicit innate immune responses in mice

“…Persistence of Brucella in the RES has been modelled successfully in the mouse, which recapitulates several key features of natural infections, including persistence of bacteria for at least 5 months (Stevens et al ., 1994), localization of bacteria to cells with macrophage‐like morphology (Meador et al ., 1986) and splenomegaly (Birmingham and Jeska, 1981). Use of this experimental model has also facilitated genomic screens to identify the virulence mechanisms used by Brucella to establish persistent infection (Hong et al ., 2000; Lestrate et al ., 2000; 2003; Haine et al ., 2005).…”

Collaboration of bovine T lymphocytes and macrophages in T-lymphocyte response to Brucella abortus

“…In vivo development of nonspecific resistance to B. abortus-infected mice has been described in several studies (5,13), and these reports have suggested that activated macrophages are responsible for the antibacterial activity. There are also studies in which heightened bactericidal activity has been shown in vitro by macrophages collected from B. abortus-infected mice and cattle (3,11,29). Most recently, in studies in which B. abortusinfected mice have been examined, increased macrophage activation has been reported by several criteria, including spreading, Fc and C3 receptor density, locomotion, and chemotactic responsiveness (3).…”

“…There are also studies in which heightened bactericidal activity has been shown in vitro by macrophages collected from B. abortus-infected mice and cattle (3,11,29). Most recently, in studies in which B. abortusinfected mice have been examined, increased macrophage activation has been reported by several criteria, including spreading, Fc and C3 receptor density, locomotion, and chemotactic responsiveness (3). However, in these in vivo and in vitro studies done by others, interactions between bovine macrophages and T lymphocytes in response to B. abortus have not been examined.…”