Today we will discuss the constituents and the mechanism of innate immunity in mammals. Once the barriers are breached, other components of the innate immune system take over. Phagocytic cells are the most important component of the innate immune attack on bacterial invaders. The transit of cells from blood to tissue is called extravasation and has four steps.
Neutrophils are among the first cells to respond in a bacterial infection.
They are a major component of pus. If the pathogens makes it directly to the blood, there are circulating molecules that can help clear them.