ABSTRACT

T he importance of macrophages in the host response to infection has been recognised for decades. However, the macrophage has a range o f phenotypes, functions and activation states and consequendy the study of macrophage biology is complicated by the heterogeneity of these cells. An understanding of basic macrophage biology is required to understand the mechanisms of evasion, invasion and subversion of macrophage defences by protozoan pathogens. Herein we review the origins of macrophages, differences in macrophage phenotypes, mechanisms of macrophage based killing and subversion of this killing by pathogens.