Innate and Adaptive Immunity: Types of Immune Responses (Full version)

every day we're exposed to countless pathogens but don't get sick every time so how does the body recognize and fight these pathogens let's discuss this step by step the first physical line of defense is provided by the skin and mucous membranes in the airways mucous ciliary motion and coughing are important defense mechanisms

in addition bodily secretions also protect us from pathogens for example saliva contains lysozyme which can destroy the cell wall of gram-positive bacteria if we take a look at the stomach gastric acid creates a hostile environment for most bacteria also the normal flora residing on the skin and mucous membranes displace and fight pathogens

if the pathogen ends up breaching these barriers the body depends on further active defense mechanisms of the immune system first the cells involved in innate immunity become active certain stimuli such as tissue injury trigger an inflammatory reaction as a result leukocytes especially granulocytes and macrophages are attracted to the site of damage they

leave the adjacent blood cells and penetrate into the damaged tissue the body recognizes certain specific repeating patterns present on many pathogens as foreign these include for example lipopolysaccharides which are located on the outer membrane of gram-negative bacteria these characteristics are also called pathogen-associated molecular patterns in short pamps because they're commonly shared between different pathogen

subtypes they're considered non-specific the macrophages and granulocytes attracted by the inflammation recognize the pamps of pathogens through pattern recognition receptors in short prr the granulocytes then secrete a toxic substance to fight against the invading bacteria the macrophages engulf the bacteria or in other words phagocytose them in addition pamps activate the complement system