The foreign body reaction (FBR) is the final stage of the inflammatory and wound healing responses following the implantation of a medical device, prosthesis, or biomaterial. It involves macrophages and foreign body giant cells (FBGCs) and is influenced by the chemical, physical, and morphological properties of the biomaterial surface. The FBR includes events such as protein adsorption, monocyte/macrophage adhesion, macrophage fusion to form FBGCs, and interactions between macrophages/FBGCs and inflammatory/wound healing cells. Biomaterial surface properties significantly modulate the FBR in the first two to four weeks after implantation, even though the FBR persists throughout the device's in vivo lifetime. Understanding the FBR is crucial for ensuring the biocompatibility and safety of medical devices, as it can impact short- and long-term tissue responses. The FBR is also influenced by the incorporation of biological components such as allogeneic or xenogeneic cells and stem cells into tissue-engineered constructs, which presents new challenges. The immune system's interaction with these cells and the influence of biomaterials or tissue-engineered constructs on these interactions are critical for the safety, biocompatibility, and function of the device or system. The FBR is characterized by the presence of mononuclear cells, including monocytes and lymphocytes, at the implant site. Chronic inflammation is often associated with the FBR, where monocytes, macrophages, and FBGCs are present at the biomaterial interface. The FBR can lead to the formation of a fibrous capsule around the implant. Macrophage adhesion and fusion are influenced by integrin receptors, which mediate cell-extracellular matrix interactions. The FBR can also lead to the degradation of biomaterials, which may result in device failure. The degradation is mediated by macrophages and FBGCs, which release degradative agents such as reactive oxygen intermediates, degradative enzymes, and acid. The FBR is also influenced by the surface chemistry of the biomaterial, which can affect the adhesion and apoptosis of macrophages. The FBR can lead to the formation of FBGCs, which are multinucleated cells formed from the fusion of monocyte-derived macrophages. The FBR is also influenced by cytokine secretion, which can modulate the inflammatory and wound healing response. The FBR can lead to the remodeling of the extracellular matrix, which is important for tissue healing. The FBR is a complex process that involves multiple cellular and molecular interactions, and understanding it is essential for the development of biocompatible medical devices and tissue-engineered constructs.The foreign body reaction (FBR) is the final stage of the inflammatory and wound healing responses following the implantation of a medical device, prosthesis, or biomaterial. It involves macrophages and foreign body giant cells (FBGCs) and is influenced by the chemical, physical, and morphological properties of the biomaterial surface. The FBR includes events such as protein adsorption, monocyte/macrophage adhesion, macrophage fusion to form FBGCs, and interactions between macrophages/FBGCs and inflammatory/wound healing cells. Biomaterial surface properties significantly modulate the FBR in the first two to four weeks after implantation, even though the FBR persists throughout the device's in vivo lifetime. Understanding the FBR is crucial for ensuring the biocompatibility and safety of medical devices, as it can impact short- and long-term tissue responses. The FBR is also influenced by the incorporation of biological components such as allogeneic or xenogeneic cells and stem cells into tissue-engineered constructs, which presents new challenges. The immune system's interaction with these cells and the influence of biomaterials or tissue-engineered constructs on these interactions are critical for the safety, biocompatibility, and function of the device or system. The FBR is characterized by the presence of mononuclear cells, including monocytes and lymphocytes, at the implant site. Chronic inflammation is often associated with the FBR, where monocytes, macrophages, and FBGCs are present at the biomaterial interface. The FBR can lead to the formation of a fibrous capsule around the implant. Macrophage adhesion and fusion are influenced by integrin receptors, which mediate cell-extracellular matrix interactions. The FBR can also lead to the degradation of biomaterials, which may result in device failure. The degradation is mediated by macrophages and FBGCs, which release degradative agents such as reactive oxygen intermediates, degradative enzymes, and acid. The FBR is also influenced by the surface chemistry of the biomaterial, which can affect the adhesion and apoptosis of macrophages. The FBR can lead to the formation of FBGCs, which are multinucleated cells formed from the fusion of monocyte-derived macrophages. The FBR is also influenced by cytokine secretion, which can modulate the inflammatory and wound healing response. The FBR can lead to the remodeling of the extracellular matrix, which is important for tissue healing. The FBR is a complex process that involves multiple cellular and molecular interactions, and understanding it is essential for the development of biocompatible medical devices and tissue-engineered constructs.