Ebook The immune system (4th edition): Part 2
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Ebook The immune system (4th edition): Part 2
2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2ll. For these microbes, the human body constitutes a vast resource-rich environment in which to live and reproduce. In facing such threats, the body deploys a variety of defense mechanisms that have accumulated over hundreds of millions of years of Invertebrate and vertebrate evolution. In consideri Ebook The immune system (4th edition): Part 2ng mechanisms of innate immunity in Chapters 2 and 3 and of adaptive immunity in Chapters 4-11, we principally used the example of a bacterial pathogeEbook The immune system (4th edition): Part 2
n that enters the body through a skin wound, causing an Innate Immune response in the infected tissue that then leads to an adaptive immune response i2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2, infection, and Inflammation. Until recently, these were the only responses studied by most immunologists, who usually administered their experimental antigens by subcutaneous injection. But in the real world, only a fraction of human infections are caused by pathogens that enter the body's tissues Ebook The immune system (4th edition): Part 2 by passage through the skin. Many more infections, Including all of those caused by viruses, make their entry by passage through one of the mucosal sEbook The immune system (4th edition): Part 2
urfaces. Although the immune response to Infection of mucosal tissue has strategies and principles in common with those directed at Infections of skin2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2 of the extent of these differences has led to the concept that the human immune system actually consists of two seml-autonomous parts: the systemic immune system, which defends against pathogens penetrating the skin, and the mucosal immune system, which defends against pathogens breaching mucosal s Ebook The immune system (4th edition): Part 2urfaces. This chapter focuses on mucosal immunity and how It differs from systemic immunity.10-1 The communication functions of mucosal surfaces rendeEbook The immune system (4th edition): Part 2
r them vulnerable to infectionMucosal surfaces or the mucosae (singular mucosa) are found throughout much of the body, except the limbs, but they are 2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2gives them their name. Mucus contains glycoproteins, proteoglycans, peptides, and enzymes that protect the epithelial cells from damage and help to limit infection. Mucosal epithelia line the gastrointestinal, respiratory, and urogenital tracts, and are also present in the exocrine glands associated Ebook The immune system (4th edition): Part 2 with these organs: the pancreas, the conjunctivae and lachrymal glands of the eye, the salivary glands, and the mammary268 Chapter 10: Preventing InfEbook The immune system (4th edition): Part 2
ection at Mucosal SurfacesFigure 10.1 Distribution of mucosal tissues. This diagram of a woman shows the mucosal tissues. The mammary glands are a muc2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2tal tract; orange, secretory glands.glands of the lactating breast (Figure 10.1). These tissues are all sites of communication, where material and information are passed between the body and its environment. Because of their physiological functions of gas exchange (lungs), food absorption (gut), sen Ebook The immune system (4th edition): Part 2sory activity (eyes. nose, mouth, and throat), and reproduction (uterus, vagina, and breast), the mucosal surfaces are by necessity dynamic, thin, perEbook The immune system (4th edition): Part 2
meable barriers to the interior of the body. These properties make the mucosal tissues particularly vulnerable to subversion and breach by pathogens. 2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2f a person’s mucosal surfaces is vastly greater than that of the skin: the small intestine alone has a surface area 200 times that of the skin. Reflecting this difference, three-quarters of the body's lymphocytes and plasma cells are to be found in secondary lymphoid tissues serving mucosal surfaces Ebook The immune system (4th edition): Part 2. A similar proportion of all the antibodies made by the body is secreted at mucosal services as the dimeric form of IgA, also known as secretory IgAEbook The immune system (4th edition): Part 2
or SlgA (see Chapter 9). A distinctive feature of the gut mucosa Is Its constant contact with the large populations of commensal microorganisms that i2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2ids derived from the plants and animals that contribute to our diet. In this situation, the major challenge is to make immune responses that eliminate pathogenic microorganisms and restrict the growth and location of commensal microorganisms. but do not interfere with our food and nutrition. As most Ebook The immune system (4th edition): Part 2 research on mucosal immunity has been on the gut, this will provide our principal example of a mucosal tissue, but first we will examine the constituEbook The immune system (4th edition): Part 2
ents and properties of the mucus.10-2 Mucins are gigantic glycoproteins that endow the mucus with the properties to protect epithelial surfacesIn ever2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2layer provides a formidable barrier that prevents commensal and pathogenic organisms from gaining access to the Internal Issues. Adding to this defense Is the mucus, which prevents microorganisms and other environmental material. such as smoke and smog particles, from gaining access to the epitheliu Ebook The immune system (4th edition): Part 2m, lhe molecular basis for the viscosity and protective properties of mucus is a family of glycoproteins called mucins that are secreted by the epitheEbook The immune system (4th edition): Part 2
lium, lhese proteins are huge, their polypeptide chains reaching lengths of more than 10.000 amino acids, but they are constructed from simple sequenc2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2This carbohydrate comprises more than 70% of the weight of the much) glycoprotein. The extensive glycosylation forces the mucin polypeptides Into extended conformations. Globular domains at the ends of the polypeptides contain cysteine residues that make disulfide bonds between the stretched-out pol Ebook The immune system (4th edition): Part 2ypeptides, forming polymers and molecular networks that reach sizes greater than 1 million daltons (1 MDa) (Figure 10.2). The Intertwining of these giEbook The immune system (4th edition): Part 2
gantic proteins is what makes mucus viscous, so that it physically impedes the movement of microorganisms and particles. The extensive glycosylation o2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2ituent of the mucin giycans is sialic acid, which gives mucins a polyanionic surface. Through this they can bind the positively charged soluble effector molecules of Innate immunity, such as defenslns and other antimicrobial peptides, and of adaptive Immunity, notably secretory IgA. Bacteria negotia Ebook The immune system (4th edition): Part 2ting their way through mucus can thus be trapped by IgA and killed by defenslns. Mucosal epithelia are dynamic tissues In which the epithelial cell laEbook The immune system (4th edition): Part 2
yer turns over every 2 days or so, and mucus with Its content of microorganisms Is continuously being expelled from the body.The viscoelastic properti2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2 Into the mucus and tile extent of their cross-linking. In the human genome, seven genes encode secreted mucin polypeptides and are expressed in different mucosal tissues; an additional 13 genes encode mucin molecules that are membrane glycoproteins (Figure 10.3). These are expressed on the surface Ebook The immune system (4th edition): Part 2of epithelial cells and are not cross-linked like the secreted mucins. Although not so well characterized as the secretory mucins, these membrane muciEbook The immune system (4th edition): Part 2
ns are believed to form a mucus-like environment at the epithelial cell surface that has similar protective properties. Because they are so much bigge2b/Chapter 10Preventing Infection at Mucosal SurfacesMost infections diseases suffered by humans are caused by pathogens much smaller than a human cel Ebook The immune system (4th edition): Part 2ching microorganisms before they can Interact with other components at the surface.Preventing infection at mucosal surfaces ZbyFigure 10.2 The structure of mucins gives mucus its characteristic protective properties. Mucins secreted by goblet cells are long polypeptides densely arrayed with short ca Ebook The immune system (4th edition): Part 2rbohydrates attached to serine and threonine residues. Through cysteine residues In the globular domains at the N- and C-termlni. the mucin polypeptidEbook The immune system (4th edition): Part 2
es become cross-linked Into the gigantK extended polymeric networks that form the mucus. This unusual structure gives mucus its viscosity, which lubriGọi ngay
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