(A) Different receptors present on macrophages surfaces for sensing foreign particles. (B) Phagocytosis of microbes followed by formation of phagolysosomeand discharge of waste material. (C)The peptide fragment of degraded microbes are presented along with the help of class-II MHC on the macrophages cell surface to perform antigen presentation to lymphocytes. (D) Release of inflammatory molecules which destroy microbes present in microenvironment.
(E) Inflammation- Macrophages exposed to bacterial components or interferon-γ (IFN-γ) activateto produce wide array of inflammatory molecules to inhibit or kill pathogens (Figure 34.4). They produces reactive oxygen species (ROS) such as superoxide radical (O2-), hydrogen peroxide and reactive nitrogen intermediate (RNS) tooxidize pathogenic organism. The inflammatory molecules reduce the microbial burden in host but excess prodution leadto host tissue damage and disturb homeostasis.
(F) Tissue repair and remodeling- Macrophages play an important role in wound healing, tissue repair and remodeling.At wound site, injury results in accumulation of dead and apoptotic cells and cellular debries which will be phagocytized by macrophages. Additionally, at wound bed macrophages secrete transforming growth factor‑β (TGF-β), platelet-derived growth factor (PDGF), fibroblast growth factor-2 (FGF-2) and insulin like growth factor-1 (IGF-1) to stimulatescollagen production from fibroblast cells. Later, macrophages secrete MMPs to degrade collagen which helps fibroblast and endothelial cells to migrate at wound site for new blood vessels formation.