Host Defense Mechanisms To Protect Against Infections

Among the host defense mechanisms to protect against infections include natural barriers (eg., Skin, mucous membranes) The non-specific immune responses (eg. B phagocytic cells [neutrophils, macrophages] and their products) Specific immune responses (eg., Antibodies, lymphocytes) natural barriers skin the skin usually prevents the penetration of micro-organisms when it is not violated (eg., by wounds, intravenous catheter or surgical incision). Among the exceptions include the following: The human papilloma virus, which is able to penetrate through intact skin and cause warts Some parasites (eg, Schistosoma mansonii, Strongyloides stercoralis.). Many mucous mucous secretions are covered with the antimicrobial properties (z. B. cervical, prostate secretions and tears include lysozyme [muraminidase]. Lysozyme cleaves the Muraminsäurebrücken in the bacterial cell wall, particularly in Gram-positive bacteria). Locally formed secretions contain immunoglobulins moreover, mainly IgG and secretory IgA, which verhindern.Atemwege the binding of microorganisms to host cells of the respiratory tract has filter systems of the upper airways. When the invading pathogens reach the tracheobronchial tree, they are transported away by the mucociliary epithelium of the lung. coughing also helps to eliminate the pathogen. If pathogens penetrate into the alveoli, they are phagocytosed by alveolar macrophages and Gewebshistiozyten. wird.GI tract However, these defense mechanisms can be overcome by high numbers or by reduced effectiveness, to air pollution (eg. as cigarette smoke) or interaction with protective factors (z. B. endotracheal intubation, tracheostomy) caused to act in the gastrointestinal tract of the acidic pH of the stomach and the antibacterial activity of pancreatic enzymes, bile and intestinal secretions as a natural barrier. Peristalsis and the physiological rejection of epithelial cells remove microorganisms. If peristalsis is slowed down (z. B. due to substances such as belladonna or opium alkaloids), this will delay the defense of some pathogens and prolongs the disease process, such. As in symptomatic shigellosis. Patients with altered immune system can be predisposed to certain infections (eg. As are patients with achlorhydria particularly susceptible to salmonellosis). The physiological intestinal flora can inhibit the growth of pathogens, a change of this flora by antibiotics can lead to excessive growth of existing pathogens (eg. As Salmonella Typhimurium) or superinfection with common commensal organisms (eg. As Candida albicans) .Urogenitaltrakt genitourinary also provides in men the length of the urethra (20 cm), in women, the acidic pH in the vagina a protection factor, the increased osmotic pressure in the renal medulla. The Tamm-Horsfall protein is a glycoprotein which is produced by the kidneys and released in large quantities in the urine; some bacteria preferentially bind to it, which is why they can not settle in the urinary tract. Non-specific immune responses cytokines (u. A. IL-1, IL-6, tumor necrosis factor-alpha, interferon-gamma) are formed mainly of macrophages and lymphocytes activated in an antigen-independent and mediate acute phase reaction. As part of the reaction leads to fever and an increased release of neutrophils by the bone marrow. Endothelial cells produce large amounts of IL-8, which attracts neutrophils. The inflammatory reaction attracts the immune system components to the site of injury or infection, and is characterized by increased blood supply and tissue permeability, which allows the chemotactic peptides, as well as neutrophil and mononuclear cells to leave the intravascular space. The propagation of the pathogen is by inclusion of the microorganisms by phagocytes (z. B. neutrophilic granulocytes, macrophages) limited. Phagocytes are attracted chemotactic microorganisms and devour them; then they release the contents of lysosomes, which help to destroy the microorganisms. The phagocytes form oxidative products such. As hydrogen peroxide, the total formatted kill microorganisms. If an infection on a quantitative or qualitative defect based on neutrophils, these runs extended normally and rekurrierend and speaks slowly to antibiotics. Frequently staphylococci, gram-negative pathogens and fungi are responsible for such infections. Specific immune responses, the infected host, a variety of antibodies (complex glycoproteins, also known as immunoglobulins) produce that bind to specific microbial antigenic targets. Antibodies can help kill the infecting organisms by attracting leukocytes of the host and activate the complement system. The complement system destroys the cell walls of infected organisms usually have the classic activation pathway. but the complement system can also be activated on the surface of some microorganisms via the alternative pathway. In addition, antibodies can the deposition of substances which are known as opsonins (z. B. the complement C3b), support on the surface of microorganisms, which facilitates their phagocytosis. Opsonization is important for the elimination of encapsulated bacteria such. B. pneumococcal or meningococcal. Genetic factors Many pathogens that the genes of the host affects the susceptibility of the host and the resulting morbidity and mortality. For example, have patients with deficits of terminal complement components (C5 to C8, C9 perhaps) an increased susceptibility to infections caused by Neisseria species.

Health Life Media Team

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