Components that comprise innate immunity against microbial invasion include?

• A. Physical barriers, phagocytes, natural killer cells, complement, and inflammatory mediators
• B. B cells and antibodies
• C. T cells and cytokines
• D. Red blood cells and platelets

Answer: (A)

Innate immunity provides the immediate, non-specific defense against microbes, acting as the first line of protection. The components that make this up include physical barriers such as skin and mucous membranes that block entry; phagocytes like neutrophils and macrophages that engulf and destroy invaders; natural killer cells that attack infected or abnormal cells without prior exposure; the complement system that helps lyse pathogens, marks them for destruction, and promotes inflammation; and inflammatory mediators (such as histamine and various cytokines) that increase blood vessel permeability and recruit more immune cells to the site of infection.

This combination is characteristic of innate immunity because it functions quickly and does not require prior exposure to a specific pathogen. In contrast, B cells with antibodies and T cells with cytokines are part of adaptive immunity, which provides targeted, memory-based responses. Red blood cells and platelets are not primary immune effectors, though platelets can release mediators during inflammation; they are not considered core innate immune components.

So the set that includes physical barriers, phagocytes, natural killer cells, complement, and inflammatory mediators best represents innate immunity.