How complex is our immune system
The innate immune system is encoded within an individual’s defense from birth, it acts immediately since there is no need generate or express antigens, nor memory of prior exposure. It features barriers preventing entry, systems to deal with pathogens if they enter, and a system to recruit help and isolate the pathogen.
The best way to fight infection is to prevent entry and thus intrinsic barriers play a significant factor in innate immunity. These barriers include: physical/anatomical barriers such as our skin, mechanical barriers like mucous and cilia that help trap and flush microbes out, physiological barriers like pH and temperature that do not allow an environment for microbes to thrive in, chemical barriers like fatty acids or lysozymes that can directly destroy microbes, and microbiological barriers like normal flora on our skin that take up space preventing a niche for harmful microbes to open. If the microbe is able to evade the barriers it must be identified and stopped. One way to recognize pathogens is through highly conserved structures in microbes, called PAMPs. An example of a PAMP might be a cell wall or flagella, features that are shared with a variety of pathogens but not found in host cells. Phagocytic cells within and underneath the epithelial layer have receptors on the surface that bind to constituents of bacteria, and may include the mannose receptor, scavenger receptor, or complement receptor. In this process a bacteria will bind to the macrophage’s receptor leading to phagocytosis, which in combination with a lysosome destroy the pathogen.