Interactions betweenMycoplasma mycoidessubsp.mycoidesand bovine macrophages under physiological conditions

Abstract

AbstractWe investigated the interactions of unopsonized and opsonizedMycoplasma mycoidessubsp.mycoides(Mmm) with bovine macrophagesin vitro. Mmmsurvived and proliferated extracellularly on bovine macrophage cell layers in the absence ofMmm-specific antisera. Bovine complement used at non-bactericidal concentrations did neither have opsonizing effect nor promoted intracellular survival, whereasMmm-specific antisera substantially increased phagocytosis andMmmkilling. A phagocytosis-independent uptake ofMmmby macrophages occurred at high MOIs, also found to induce the production of TNF, and both responses were unaffected by non-bactericidal doses of bovine complement. Bovine complement used at higher doses killedMmmin cell-free cultures and completely abrogated TNF responses by macrophages. These results provide a framework to identifyMmmantigens involved in interactions with macrophages and targeted by potentially protective antibodies and point towards a pivotal role of complement in the control of inflammatory responses in contagious bovine pleuropneumonia.