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- 您请求的操作仅限于组中的用户:防御机制免疫系统已经进化到可以保护我们免受一系列感染。防止感染的宿主防御包括:====自然屏障(例如[[皮肤]],粘膜)" Merck手册专业版。宿主防御感染机制。http://www.merckmanuals.com/professional/infectious-diseases/biology-of-infectious-disease/host-defense-mechanisms-against-infection。[获取日期:2016年12月23日] " ' ==== *皮肤通常可以防止入侵的微生物,除非皮肤被物理破坏或破坏(例如受伤、静脉导管或手术切口)。例外情况包括:*粘膜含有产生具有抗菌特性分泌物的粘膜(例如,宫颈粘液、前列腺液和含有溶菌酶的泪液)。局部分泌物还含有[[免疫球蛋白(Ig)|免疫球蛋白]],主要是IgG和分泌性IgA,它们阻止微生物附着在宿主细胞上。*[[呼吸系统|呼吸道]]有上呼吸道过滤器,通过纤毛粘膜上皮将入侵的微生物从肺中运送出去。咳嗽也有助于清除细菌。如果微生物到达肺泡,肺泡巨噬细胞和组织组织细胞将它们吞噬。 However, these defenses can be overcome by large numbers of organisms or by compromised effectiveness resulting from air pollutants (e.g. cigarette smoke) or interference with protective mechanisms (e.g. endotracheal intubation, tracheostomy). *GI Tract barriers include the acid pH of the stomach and the antibacterial activity of pancreatic enzymes, bile and intestinal secretions. Peristalsis also removes microorganisms and if delayed, can result in prolonged infection. Compromised GI defense mechanisms may predispose patients to particular infections (e.g. achlorhydria predisposes to salmonellosis). Normal bowel flora can inhibit pathogens; alteration of this flora with antibiotics can allow overgrowth of inherently pathogenic microorganisms (e.g. Salmonella Typhimurium) or superinfection with ordinarily commensal organisms (e.g. Candida albicans). ==== Nonspecific Immune Responses (e.g. Phagocytic Cells [Neutrophils, Macrophages] and their products)''' ''' ==== *[[Cytokines]], produced principally by macrophages and activated [[lymphocytes]], mediate an acute-phase response that develops regardless of the inciting microorganism. The response involves fever and increased production of neutrophils by the [[Bone Marrow|bone marrow]]. *Inflammatory response directs immune system components to injury or infection sites and is manifested by the increased [[blood]] supply and vascular permeability, which allows chemotactic peptides, neutrophils, and mononuclear cells to leave the intravascular compartment. *Phagocytes, which are drawn to microbes via chemotaxis, limit microbial spread through engulfment of microorganisms. Oxidative products such as hydrogen peroxide are generated by the phagocytes and kill ingested microbes. ==== Specific Immune Responses (e.g. [[Immunoglobulins (Ig)|Antibodies]], [[Lymphocytes]])''' ''' ==== *The host can produce a variety of antibodies that bind to specific microbial antigenic targets. Antibodies can help eradicate the infecting organism by attracting the host’s [[Leukocytes|WBCs]] and activating the [[Complement System|complement system]], which destroys cell walls of infecting organisms. *Antibodies can also promote the deposition of substances known as opsonins on the surface of microorganisms, which helps promote phagocytosis.