The Innate Immune System

Sydney Risen

Austin Sovell

WTL 2

2/21/16

How is it that a small subset of molecules/cells/organs are able to defend the whole body? How does the immune system become alerted that a pathogen is present, locate where the pathogen is, and attack it?

White blood cells (WBC) only make up about 0.8% of the total cells in the entire human body. However, due to their unique abilities to recognize, kill and remember pathogens, and duplicate when the body is in need, WBCs are able to miraculously defend the entire body against parasites, viruses, fungi and bacteria. The innate immune cells and adaptive immune cells work together to protect the body from these detrimental pathogens. There are also cells besides that of those associated with the immune system that attempt to keep a pathogen outside of the body; outer epithelial cells are tightly joined together. The innate immune system is able to respond quickly by popping and engulfing pathogens,

When a pathogen enters the body it is first recognized by the innate immune system. The pathogen is identified through the use of various membrane bound proteins that bind to ligands associated with non-self cells. For the identification of most bacteria, WBCs use PAMPs and TLRs. Once sentinel cells identify pathogens as non-self, they begin to send out alert signals called cytokines. Some of these cytokine are inflammatory. Inflammation notifies WBC circulating the immune system to become sticky and exit the bloodstream at the site of infection. This is called extravasation. WBCs also use the concentration gradient of cytokines to move toward toward the site of infection through a process called chemotaxis. By remodeling their cytoskeleton the WBCs move by protruding the front end of their body, adhering, then pulling their backside