University of Central Florida (UCF) MCB2004C Microbiology for Health Professionals Practice Exam 4

Innate immunity is characterized by the body's first line of defense against pathogens, which includes physical barriers as well as cellular and molecular components that respond quickly to infections. Mast cells are a key player in this type of immunity; they are found in connective tissues and play a crucial role in allergic reactions and defense against parasites. Upon activation, mast cells release various mediators, including histamine, which contributes to inflammation and helps recruit immune cells to sites of infection.

Complement proteins are another essential component of the innate immune system. They are part of a complex cascade of proteins that can be activated in response to pathogens. The complement system helps to opsonize pathogens, promote inflammation, and direct the lysis of foreign cells. This process occurs independently of prior exposure to the pathogen, distinguishing it from adaptive immunity, which requires previous exposure to an antigen to mount a response.

Thus, the involvement of both mast cells and complement proteins is a hallmark of innate immunity, making the selection for this option accurate and reflective of the underlying immunological principles.