Ebook Immunology at a glance (10th edition): Part 2
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Ebook Immunology at a glance (10th edition): Part 2
Antimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign sub Ebook Immunology at a glance (10th edition): Part 2bstances by their shape btn has no infallible way of distinguishing whether they arc dangerous (‘pathogenic* I- By and large, this approach works well to control infection, bin it docs have its unfortunate sidc.c.g. the violent immune response against foreign but harmless structures such as pollen g Ebook Immunology at a glance (10th edition): Part 2rains, etc. (sec Fig. 35).Would-be parasitic microorganisms that penetrate the barriers of skin or mucous membranes (top) have to run the gauntlet ofEbook Immunology at a glance (10th edition): Part 2
four mam recognition systems; complement (top right), phagocytic cells (centre), antibody (right) and cell-mediated immunity (bottom), togetlver with Antimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign sub Ebook Immunology at a glance (10th edition): Part 2ponses do not come into action for several days, whereas complement and phagocytic cells (innate), being everpresent. act Within minutes. There are also (top centre) specialized innate elements, such as lysozyme, interferons, etc., which act more or less non-speciftcally. much as antibiotics do. Inn Ebook Immunology at a glance (10th edition): Part 2ate molecules that have evolved to block virus infection are sometimes called restriction factors.Generally speaking, complement and antibody are mostEbook Immunology at a glance (10th edition): Part 2
active against microorganisms free in the blood or tissues, while cell-mediated responses are most active against tlrose that seek refuge in cells (lAntimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign sub Ebook Immunology at a glance (10th edition): Part 2le to evade, resist or inhibit the relevant immune mechanisms, as illustrated in the following five figures. Evasion molecules, together with those that directly damage the host, arc known as virulence factors. With increased know ledge of the Ivost and patlvogen genomes, identification of virulence Ebook Immunology at a glance (10th edition): Part 2 factors has become a top priority.60 frwnurwtcvjy tri a Gtencu. Tenth Edbco J.HI. Ptoyisr and B M Chain © 2013 Jclo Wley 4 Sons. Ltd Pubishod 2013 byEbook Immunology at a glance (10th edition): Part 2
John wtey 4 Sons. LtdEntry Many microorganisms emcr the body through wounds or bites, hut others live on the skin or mucous membranes of the intestinAntimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign sub Ebook Immunology at a glance (10th edition): Part 2pH. enzymes, mucus and other antimicrobial secretions. as well as IgA antibody (see below). The lungs, intestine, genitourinary tract and eye each have their own specialized combination of protection mechanisms.Natural antibiotics The antibacterial enzyme lysozyme (produced largely by macrophages; s Ebook Immunology at a glance (10th edition): Part 2ee Fig. 29) and defensins. a family of polypeptides with broad antimicrobial properties, produced especially at mucosal surfaces, provide protection aEbook Immunology at a glance (10th edition): Part 2
gainst many bacteria. Recent research has also discovered a whole range of molecules blocking viruses from becoming established in cells. These ‘restrAntimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign sub Ebook Immunology at a glance (10th edition): Part 2tivated directly (‘alternative pathway*) by many microorganisms, particularly bacteria, leading to their lysis or phagocytosis. The same effect can also be achieved when C3 is activated by antibody (’classic pathway’; see Fig. 6) or by mannose-binding protein.7* Helper T cells perforin several disti Ebook Immunology at a glance (10th edition): Part 2nct functions in the immune response to microbes. Some respond to ‘carrier’ determinants and stimulate antibody synthesis by B cells. Viruses, bacteriEbook Immunology at a glance (10th edition): Part 2
a, protozoa and worms have all been shown to function as fair ly strong carriers, although there are a few organisms to which the antibody response apAntimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign sub Ebook Immunology at a glance (10th edition): Part 2vity of cytotoxic T cells. The central role of T helper cells in many infections is shown by the serious effects of their destruction, e g. in AIDS (sec Fig. 28).B Antibody formation by B lymphocytes is an almost universal feature of infection, of great diagnostic as well as protective value. As a g Ebook Immunology at a glance (10th edition): Part 2eneral rule, IgM antibodies come first, then IgG and the other classes; IgM is therefore often a sign of recent infection. Al mucous surfaces, IgA isEbook Immunology at a glance (10th edition): Part 2
the most effective antibody (sec Figs 14 and 17).Blocking Where microorganisms or (heir toxins need to enter cells, antibody may block this by combiniAntimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign sub Ebook Immunology at a glance (10th edition): Part 2all work via this mechanism. as does IgA in the intestine.Phagocytosis by polymorphonuclear leucocytes or macrophages IS the ultimate fate of the majority of unsuccessful pathogens Both C3 and antibody improve this tremendously by attaching the microbe to the phagocytic cell through C3 or Fc recepto Ebook Immunology at a glance (10th edition): Part 2rs on the latter, this is known as ‘opsonization’ (see Fig. 9).Intracellular killing Once inside the phagocytic cell, most organisms are killed and deEbook Immunology at a glance (10th edition): Part 2
graded by reactive oxygen species, lysosomal enzymes, etc. (see Fig. 8). In certain cases, ‘activation* of macrophages by T cells may be needed to triAntimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign sub Ebook Immunology at a glance (10th edition): Part 2 without phagocytosis; however, it is not clear how much this actually happens in vivo.NK Natural killer cells arc able to kill many virus-infected cells rapidly, but without live specificity characteristic of lymphocytes. NK cells are activated by cells that lose expression of MHC class 1 molecules Ebook Immunology at a glance (10th edition): Part 2. a frequent characteristic of vims-infected cells and tumours that attempt to evade adaptive immune recognition in this way.Intracellular survival SeEbook Immunology at a glance (10th edition): Part 2
veral important viruses, bacteria and protozoa can survive inside macrophages, where they resist killing. Other organisms survive within cells of muscAntimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign sub Ebook Immunology at a glance (10th edition): Part 2illing of cells harbouring virus, also allogeneic (eg. grafted) cells (see Figs 21 and 39), and sometimes tumours (sec Fig. 42).Sequestration Microorganisms that cannot be killed (c.g. some mycobacteria) or products that cannot be degraded (e.g. streptococcal cell walls) can be walled off by the for Ebook Immunology at a glance (10th edition): Part 2mation of a granuloma by macrophages and fibroblasts, aided by T"-mediated immune responses (sec Figs 21 and 37).Spread Successful microorganisms mustEbook Immunology at a glance (10th edition): Part 2
be able to leave the body and infect another one. Coughs and sneezes, faeces and insect bites arc the most common modes of spread.Persistence Some veAntimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign sub Ebook Immunology at a glance (10th edition): Part 2wn. Needless to say. these constitute some of the most chronic and intractable infectious diseases. Major strategies for immune evasion include resistance to phagocytosis and/or intracellular killing, antigenic variation, immunosuppression and various forms of concealment.Inflammation Although some Ebook Immunology at a glance (10th edition): Part 2microorganisms cause tissue damage directly (e g. cytopathic viruses or the toxins of staphylococci), it is unfortunately ttue that much of the tissueEbook Immunology at a glance (10th edition): Part 2
damage resulting from infection is due to the response of the host. Acute and chronic inflammation arc discussed in detail elsewhere (sec Figs 7 and Antimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign sub Ebook Immunology at a glance (10th edition): Part 2s or to limit tissue damage and allow some of live organisms to survive. Given enough time, natural selection should arrive at the balance that is most favourable for both parasite and host survival.virulence factors include toxins, adhesion factors, resistance factors for antibiotics, enzymes that Ebook Immunology at a glance (10th edition): Part 2destroy immunological molecules, cytokine inhibitors, antigenic variation. Successful pathogens often possess many of these.Antimicrobial immunity: aEbook Immunology at a glance (10th edition): Part 2
general scheme Potentially useful Immunity 61Immunity to virusesENTRY VIARECEPTORI \\ DIRECTY SPREAD "INTERFERONMACI protectionAntimicrobial immunity: a general schemeAt this point the reader will appreciate that the immune system is highly efficient at recognizing foreign subGọi ngay
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