Macrophages are a functionally heterogeneous group of cells with specialized
functions depending not only on their subgroup but also on the function of the organ or tissue
in which the cells are located. The concept of macrophage phenotypic heterogeneity has been
investigated since the 1980s, and more recent studies have identified a diverse spectrum of
phenotypic subpopulations. Several types of macrophages play a central role in the response
to infectious agents and, along with other components of the immune system, determine the
clinical outcome of major infectious diseases. Here, we review the functions of various
macrophage phenotypic subpopulations, the concept of macrophage polarization, and the
influence of these cells on the evolution of infections. In addition, we emphasize their role in
the immune response in vivo and in situ, as well as the molecular effectors and signaling
mechanisms used by these cells. Furthermore, we highlight the mechanisms of immune
evasion triggered by infectious agents to counter the actions of macrophages and their
consequences. Our aim here is to provide an overview of the role of macrophages in the
pathogenesis of critical transmissible diseases and discuss how elucidation of this relationship could enhance our understanding of the host?pathogen association in organ-specific
immune responses
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