The Innate Immune System
From MyMCAT
Contents |
Introduction
The innate immune system is primarily focused on the broader aspects of immune protection. While it cannot target specific pathogens, it is able to protect our body against a vast range of groups of invaders by targeting classical patterns of pathogenesis such as bacterial cell walls, flagella, unmethylated-DNA and other such elements that do not exist in our own cells. The major components of the innate immune system include: skin, digestive enzymes and hostile environments, phagocytic cells, and specific proteins in the circulatory system.
(For a full list of materials on the immune system, please visit Category:The Immune System.)
The Components of the Innate Immune System
Skin, mucosal, and other epithelial surfaces
Skin, which covers almost our entire body is designed to resist the entry of pathogens. By being many layers thick, dry, and continuously shedding, it becomes extremely difficult for bacteria to attach and migrate through. Furthermore, the wet surfaces found in our bodies (the mucosal layers of our mouth and GI tract) often secrete specific enzymes and proteins that make it difficult for bacterial to proliferate.
Hostile Environments
The digestive tract is a relatively simple mode of entry into our body- we eat millions of bacteria with every meal. The first digestive organ however, the stomach, is extremely acidic and along with digestive enzymes, makes it extremely difficult for bacteria to proliferate.
Phagocytic cells
Waiting below the surface of our skin and found throughout all of the tissues of the body are phagocytic cells capable of recognizing unusual signals and engulfing any potential invaders. This immune cells have receptors which respond to flagella, cell walls, unusual sugars, and other "patterns of pathogenesis" and trigger the cell to engulf and if possible digest the pathogen. (Classically the receptors are known as Toll-like receptors.)
Blood Components
Throughout the circulatory system are numerous proteins which can act to prevent the spread and proliferation of bacteria and target immune cells to them. This system, known as the Complement system, contains numerous proteins which when activated, trigger a cascade of enzymatic and protein binding events to disable bacteria. Some of these events include coating the surface of pathogens to neutralize them or forming pores in their membranes to induce lysis.
The Events of Injury
When pathogens to break the protective surfaces of our body, the local tissues which become infected and damaged respond by releasing a series of chemicals to induce the immune system to begin attacking the invaders. Inflammation is the first response, which begins by the damaged tissues releasing histamines and prostaglandins. These trigger blood vessels in the region to dilate and become permeable. These changes allow fluid to enter the region causing swelling and permitting the entry of macrophages. This response is primarily used to block the spread of the infection and allow immune cells to begin attacking.
