Characteristics of Suppressor Macrophages Induced by Mycobacterial and Protozoal Infections in relation to Alternatively Activated M2 Macrophages

Figure 1

Cytokine networks in hosts with mycobacterial infection. In this cytokine network, proinflammatory cytokines, including IL-12, IL-23, IL-18, and tumor necrosis factor-α (TNF-α), which are produced by infected macrophages (MΦs) and dendritic cells (DCs), induce the cellular expansion and differentiation of Th1 cells, resulting in enhanced production of Th1 and Th1-like cytokines, such as interferon-γ (IFN-γ), IL-2, TNF-α, and granulocyte-macrophage colony-stimulating factor (GM-CSF). These cytokines play crucial roles in the expression of host resistance against mycobacterial infections. In addition, immunosuppressive cytokines and humoral factors, such as IL-4, IL-10, transforming growth factor-β (TGF-β), and prostaglandin E (PGE), which are produced by Th2 cells, Treg cells, Th3 cells, and macrophages, appear to play important roles in the establishment of immunodeficiency frequently encountered in persistent and advanced infection with mycobacterial pathogens, including MTB.