Final answer:
The cell type that initiates inflammatory responses is the macrophage, which can phagocytize pathogens and release inflammatory chemicals. Mast cells are involved in type I and type II hypersensitivity reactions.
Step-by-step explanation:
Initiators of Inflammatory Responses
The cell type that initiates inflammatory responses to infection or tissue damage is the macrophage. Macrophages are a type of white blood cell that engulf and digest cellular debris, foreign substances, microbes, cancer cells, and anything else that does not have the types of proteins specific to healthy body cells on its surface. This process of ingestion is known as phagocytosis. Macrophages also release chemicals that promote inflammation, which is a component of the innate immune system's first line of defense against pathogens.
In relation to other questions listed, the macrophage is also the cell that can phagocytize pathogens and is implicated in type III hypersensitivities due to the accumulation of immune complexes in tissues and small blood vessels. Mast cells, on the other hand, are involved in type I and type II hypersensitivity reactions by releasing histamines and other mediators, whereas type II reactions specifically are characterized by antibodies mediating cell lysis or cytotoxicity.