Host Innate Immunity

Host innate immunity refers to the body's first line of defense against invading pathogens. It is a non-specific, rapid response system that is present from birth and acts immediately or within hours of an infection or injury. Unlike adaptive immunity, which tailors its response to specific pathogens and develops memory, innate immunity responds in the same way to all foreign invaders. Key functions include immediate defense, recognizing and removing foreign substances, recruiting immune cells, activating the complement cascade, acting as physical/chemical barriers, and stimulating adaptive immunity. Major components are physical barriers (skin, mucous membranes), chemical barriers (enzymes, stomach acid), cellular defenses (neutrophils, macrophages, NK cells), and humoral factors (complement, cytokines). Pattern recognition receptors (PRRs) like TLRs, CLRs, NLRs, and RLRs detect pathogens. A hallmark feature is inflammation.