Final answer:
Macrophages use pseudopodia to engulf invading microorganisms, serve as a key part of the immune system, and release cytokines to orchestrate an immune response.
Step-by-step explanation:
Macrophages, which are key players in the immune system, extend structures called pseudopodia to surround and engulf invading microorganisms. Originating from monocytes, macrophages display amoeboid movement and migrate through tissues, using pseudopodia to move and to phagocytize foreign material, including infectious agents. They not only consume pathogens and cellular debris, but also release cytokines and chemotactic substances to recruit and activate other immune cells to the site of an infection.