Chapter 7
Subject
Innate Immunity Inflammation and Wound Healing
Phago (eat)- Cytes (cell)
The Two Main Phagocytes
1. Neutrophils: The "Infantry." They are the first to arrive at the site of injury. They eat
bacteria and then die, creating what we see as pus.
2. Macrophages: The "Heavy Clean-up Crew." They arrive a bit later. They are bigger, live
longer, and can eat much more than neutrophils. They also "clean up" the dead neutrophils
and cell debris.
The Science: 4 Steps of Phagocytosis
1. Recognition and Adherence (The "Lock")
The phagocyte has to "grab" the germ. This is hard because germs are slippery.
● The Science: This is where the Complement System (C3b) comes in. It coats the germ in a process
called Opsonization. The phagocyte has receptors that lock onto the C3b like a key into a lock.
2. Engulfment (The "Swallow")
Once the phagocyte has a grip, it reaches out with arm-like extensions called pseudopods.
● The Science: It wraps its cell membrane around the germ, pulling it inside into a "storage bubble"
called a Phagosome.
3. Fusion with Lysosome (The "Stomach Acid")
Inside the phagocyte, there is another bubble called a Lysosome.
