Macrophages are adept at combating viruses, bacteria, and protozoa capable of living within the cells of the host. Meanwhile, neutrophils hold the fort against pyogenic (pus-forming) bacteria. It is thus no small irony that certain viruses, such as HIV, hijack macrophages for their home base.
Neutrophils tote a variety of toxic substances that kill or inhibit the growth of bacteria and fungi. Like macrophages, neutrophils pummel pathogens via ROS respiratory burst.
Neutrophils are the most abundant phagocyte, accounting for 50–60% of the total circulating leukocytes. Neutrophils are typically first on the scene at an infection.
A healthy adult produces more than 100 billion neutrophils per day. During acute inflammation, the bone marrow factory pumps out over a trillion neutrophils a day, 10 times the nominal production level.