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The waxy cuticle of most leaves, the exoskeleton of insects, the shells and membranes of externally deposited eggs, and skin are examples of mechanical barriers that are the first line of defense against infection. [8] Organisms cannot be completely sealed from their environments, so systems act to protect body openings such as the lungs ...
The epithelial surfaces form a physical barrier that is impermeable to most infectious agents, acting as the first line of defense against invading organisms. [3] Desquamation (shedding) of skin epithelium also helps remove bacteria and other infectious agents that have adhered to the epithelial surface.
Innate immunity, also known as native immunity, is a semi-specific and widely distributed form of immunity. It is defined as the first line of defense against pathogens, representing a critical systemic response to prevent infection and maintain homeostasis, contributing to the activation of an adaptive immune response. [4]
A large number of immune system cells in the intestines are found in dome-like structures called Peyer’s patches and in small mucosal lymphoid aggregates called cryptopatches. [14] Above the Peyer’s patches is a layer of epithelial cells, which together with the mucus form a barrier against microbial invasion into the underlying tissue ...
Complement proteins are proteins that play a role in the non-specific immune responses alongside these non-specific immune cells to make up the first line of immune defense. [4] The non-specific immune response is an immediate antigen-independent response, however it is not antigen-specific. Non-specific immunity results in no immunologic memory.
Neutrophils are the immune system's first line of defense against infection and have conventionally been thought to kill invading pathogens through two strategies: engulfment of microbes and secretion of anti-microbials. In 2004, a novel third function was identified: formation of NETs.
The skin microbiota is vital as a line of defense against infection, a physical barrier between the environment and the inside of the host. Commensal microbes that live on the skin, such as Staphylococcus epidermidis , produce antimicrobial peptides (AMPs) that aid the host immune system. [ 24 ]
The first line of defense, known as the innate immune system, is meant to prevent initial pathogenic entry and establishment. The innate immune system is only broadly specific to pathogens and includes: anatomical barriers, inflammation , phagocytosis , and nonspecific inhibitors.