**Abstract**

When the first line of defence—the integumentary system fails, the immune system protects us from infections by pathogens. Macrophages are crucial for mediating effects in the innate immune system by eliminating impaired cells and harmful micro-organisms through phagocytosis. Although other cells undergo phagocytosis, the cellular processes that regulate phagocytosis may vary from cell to cell. These include metabolic changes, signal transduction, and changes in molecular expression or post-translational modifications. This chapter will comprehensively review biological processes that regulate phagocytosis in macrophages, including; changes in metabolic processes, signal transduction, molecular expression, and post-translational modifications.

**Keywords:** macrophage, innate immunity, phagocytosis, regulation, receptors
