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Microbiology Exam 4#

Akasya Benge Microbiology English 88 cards

Cards in this deck (88)

  1. 1Locations of barriersSkin, Mucosae (digestive tract, respiratory tract, reproductive tract, conjunctiva of eyes), Physical barriers, protective secretions, presence of normal microbiota, mechanical removal
    Within the body, iron is sequestered to restrict microbial growth
  2. 2Lysozymetears, sweat, saliva
  3. 3Antimicrobial peptides (pore-forming)digestive tract, lungs, vagina
  4. 4Lactoferrin(sequesters iron): lungs, milk, saliva, tears, nasal mucus
  5. 5Defensive response to tissue damageFacilitates immune reaction and sealing \of damaged area
    Chronic inflammation may cause damage to tissue, interfere with proper repair
  6. 63 signs & 1 symptomRedness
    Swelling
    Warmth
    Pain
  7. 7Phagocytesclass of cells that specialize in consuming microbes and extracellular debris
  8. 8Antibodies (green)made by specific immune system
  9. 9Vasodilationfacilitates the supply of circulating proteins and cells in blood to the damaged tissue
  10. 10Cytokineschemical messengers between immune cells and tissues
  11. 11Interleukinscytokins of white blood cells
  12. 12PAMPspathogen-associated molecular patterns)
  13. 13Receptors for PAMPs are...PRRs (pattern recognitions receptors
  14. 14Mannose-Binding Lectin & C-reactive proteinSoluble receptors
    Circulate in extracellular fluids, bind to ligands on exterior of various microbesAct as opsonins: make it easier for receptors on phagocytes to bind the microbe and phagocytose it
  15. 15PhagocytesNeutrophils, monocytes, macrophages
  16. 16Neutrophilsfirst phagocytic responders of nonspecific immunity
  17. 17Monocytescirculate in blood
  18. 18Macrophagesdevelop from monocytes when they leave blood for tissue; more powerful phagocytosis, cross-activated by specific immune system
  19. 19Fixed macrophagespermanently staged at key points in the body (lungs, liver, etc.)
  20. 20Wandering macrophagesmove around through extracellular fluid and tissues
  21. 21Eosinophilbinds to tails of antibodies bound to parasites, degranulates and releases toxic materials (form pores in parasite)
  22. 22Basophilmobile in blood, degranulates to release histamine and pro-inflammatory chemicals (triggered by antibodies or complement system)
  23. 23Mast cellsimilar to basophil, but fixed in connective tissue
  24. 24MHCmajor histocompatibility complex
    Displays peptide fragments at cell surface to be bound by other receptors
  25. 25MHC I is...and...on all cells, Peptide fragments from proteins broken down inside cell (in lysosome) are displayed on MHC I—regularly renewed, shows what proteins are being recycled inside every cell
  26. 26MHC II is...on a specific subset of immune cells
  27. 27Evasion methodsCapsules limit the ability of the immune system to recognize and bind
    Enzymes can degrade circulating immune components, such as antibodies, or hijack them (Staphylococcus aureus Protein A)
    Antigen remodeling: some microbes (e.g., trypanosomes, protozoa causing sleeping sickness and leishmaniasis) swap out surface antibodies every few generations so that they evade immune response as it begins to ramp up
  28. 28Attachment methodsFimbriae
    Various adhesive proteins
    Tir (in certain strains of E. coli) delivered by Type III secretion system; when engaged by E. coli surface protein, triggers cytoskeletal remodeling
  29. 29Type III and IV secretion systemsAssociated with Gram-negative bacteria
    Type IV is related to conjugation systems (pili)
    Inject proteins from bacterium into target cell
    May be toxic or otherwise alter host cell behavior
    Can be injected across plasma membrane or from interior of endosome to cytoplasm
  30. 30SalmonellaSecretion systems inject bacterial proteins that trigger phagocytosis (from outside) and block phagosome-lysosome fusion (from inside)
  31. 31EndotoxinPresent in Gram-negative outer membrane
    Released at binary fission or lysis
    Powerfully inflammatory-can cause septic shock
  32. 32Shiga ToxinB subunit engages receptor found on epithelium of kidney, epithelium of blood vessels
    Damages organs with many tiny blood vessels when they clog with disintegrating endothelium (glomerular capillaries, microvasculature of the brain, etc.)
  33. 33ToxoidsHeat-denatured forms of toxins
    Still retain key epitopes for recognition
    Induce immune response; memory B cells will be able to reactivate and produce antibody that neutralizes the toxin
  34. 34CytolysinsBacterial peptides; usually form pores in plasma membranes of host cells (lecithinases degrade phospholipids themselves)
    Like toxins, may be specific for particular cell types
    Death may cause due to generalized lysis or because pore disrupts homeostasis of a particular chemical (e.g., cytosolic Ca2+)
    Some cytolysins are triggered by the acidification of the endosome and release endocytosed bacteria into cytosol
  35. 35SuperantigensSuperantigen triggers activation of many random native TH cells
    Clonal expansion leads to production of many short-lived effectors with no target
    “Cytokine storm” leads to massive systemtic inflammation
  36. 36Tissue penetration in Streptococcus pyogenesHyaluronidase-degrades hyaluronic acid of connective tissues
    Streptokinase-degrades blood clots
  37. 37T-cell immune receptors (TCRs)in membrane of individual T cells
  38. 38B-cell immune receptors (BCRs)in membrane of individual B cells
  39. 39Immunoglobulins (Igs) or antibodiessoluble, otherwise similar to BCRs
  40. 40Ligands of these receptors are antigensTypically proteins or glycoproteins
    Recognize a unique 3-D surface/charge distribution (epitope) on antigen
    Binding has high affinity (sticks tight) and specificity (does not stick to other things)
  41. 41Dendritic cells (DCs)Embedded throughout body tissues
    Constantly phagocytosing small amounts of antigen
    When they detect inflammatory cytokines, they stop phagocytosis, move to a lymph node, and present their collection of antigens on MHC II to naïve TH cells
  42. 42IgMfirst form secreted. Activates complement, forms large cross-linked immune complexes. Mostly in blood or inflamed tissue, occasionally on mucosa
  43. 43IgGmain form of antibody in blood; can cross placenta, etc. Complement activator, ADCC, opsonization
  44. 44IgAmainly secreted into mucus; low levels in blood. Good at neutralization, some ADCC. Does not promote inflammation.
  45. 45IgEantiparasitic. “Pre-loads” on mast cells & basophils: antiparasitic response and allergies. Targets ADCC by eosinophils
  46. 46VaccinesMay consist of killed whole microbe, attenuated live microbe, or purified microbial components
    Adjuvant may be required to help trigger inflammation and force a stronger reaction to the antigen(s) in the vaccine
    Longer dwell time and uptake by APCs may induce more memory cells
    Typical vaccine efficacy is 85-90%
  47. 47Describe the physical barriers to infection in different parts of the body. What features make skin and mucosa resistant to infection? How do the normal microbiota help prevent attachment and infection? What is the significance of iron in the growth of pathogens?Skin, Mucosae (digestive tract, respiratory tract, reproductive tract, conjunctiva of eyes),
    Physical barriers, protective secretions, presence of normal microbiota, mechanical removal
    Normal microbiota takes up all resources so new bacteria (infectious) cannot grow.
    Within the body, iron is sequestered to restrict microbial growth
  48. 48Describe the inflammatory response. How is it triggered? How does it help the body fight infection? Why can it be detrimental?The inflammatory response (inflammation) occurs when tissues are injured by bacteria, trauma, toxins, heat, or any other cause. The damaged cells release chemicals including histamine, bradykinin, and prostaglandins. These chemicals cause blood vessels to leak fluid into the tissues, causing swelling. This helps isolate the foreign substance from further contact with body tissues.
    The chemicals also attract white blood cells called phagocytes that "eat" germs and dead or damaged cells. This process is called phagocytosis. Phagocytes eventually die. Pus is formed from a collection of dead tissue, dead bacteria, and live and dead phagocytes.
    Many of the body's immune cells cluster around the intestines. Most of the time, those immune cells ignore the trillions of healthy bacteria that live in the gut. But for some people, that tolerance seems to be broken, and their immune cells begin to react to the bacteria, creating chronic inflammation.
    Chronic inflammation can lead to a number of disorders, including IBD, depression, arthritis, bone loss, inability to lose weight and interfering
  49. 49Pathogen Associated Moleculer PatternPAMPs activate innate immune responses, protecting the host from infection, by identifying some conserved nonself molecules. Bacterial lipopolysaccharides (LPSs), endotoxins found on the cell membranes of gram-negative bacteria, are considered to be the prototypical class of PAMPs.
  50. 50Pattern recognition receptors (PRRsplay a crucial role in the proper function of the innate immune system. PRRs are germline-encoded host sensors, which detect molecules typical for the pathogens.[2] They are proteins expressed, mainly, by cells of the innate immune system, such as dendritic cells, macrophages, monocytes, neutrophils and epithelial cells,[3][4] to identify two classes of molecules: pathogen-associated molecular patterns (PAMPs), which are associated with microbial pathogens, and damage-associated molecular patterns (DAMPs), which are associated with components of host's cells that are released during cell damage or death.
  51. 51What is the main PRR in the vertebrate immune system?TLR
  52. 52C-reactive proteinCRP binds to phosphocholine on micro-organisms. It is thought to assist in complement binding to foreign and damaged cells and enhances phagocytosis by macrophages (opsonin-mediated phagocytosis), which express a receptor for CRP. It plays a role in innate immunity as an early defense system against infections.
  53. 53Lectinsin the immune system, lectins recognize carbohydrates found specifically on pathogens, or those that are not recognizable on host cells. Clinically, purified lectins can be used to identify glycolipids and glycoproteins on an individual's red blood cells for blood typing.
  54. 54Describe the activity of the complement system. Where are its proteins found? What triggers the activation of the complement cascade? What are its major effectsThe complement system is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promotes inflammation, and attacks the pathogen's cell membrane. The complement system consists of a number of small proteins found in the blood, synthesized by the liver, and circulate as inactive precursors. When stimulated by one of several triggers, proteases in the system cleave specific proteins to release cytokines and initiate an amplifying cascade of further cleavages.
  55. 55What are the two Type I interferons and what are their effects?IFN-α, IFN-β
    are a large subgroup of interferon proteins that help regulate the activity of the immune system.
    Interferons bind to interferon receptors. All type I IFNs bind to a specific cell surface receptor complex known as the IFN-α receptor (IFNAR) that consists of IFNAR1 and IFNAR2 chains.
    Type I IFNs are found in all mammals, and homologous (similar) molecules have been found in birds, reptiles, amphibians and fish species.
  56. 56IFN-αThe IFN-α proteins are produced mainly by plasmacytoid dendritic cells (pDCs). They are mainly involved in innate immunity against viral infection. IFN-α is also made synthetically as medication in hairy cell leukemia.
  57. 57IFN-βThe IFN-β proteins are produced in large quantities by fibroblasts. They have antiviral activity that is involved mainly in innate immune response. IFN-β1 is used as a treatment for multiple sclerosis as it reduces the relapse rate. IFN-β1 is not an appropriate treatment for patients with progressive, non-relapsing forms of multiple sclerosis.
  58. 58List and describe the cells involved in innate immunity. What is the function of each one?Natural killer cells, mast cells, eosinophils, basophils; and the phagocytic cells include macrophages, neutrophils, and dendritic cells, and function within the immune system by identifying and eliminating pathogens that might cause infection
  59. 59Describe the process by which phagocytes engulf and destroy microbesBoth macrophages and neutrophils are drawn toward an area of infection or inflammation by means of substances given off by the bacteria and the infected tissue or by a chemical interaction between the bacteria and the complement system of blood serum proteins. Neutrophils may also engulf particles after colliding with them accidentally.
    Before phagocytosis is accomplished, the phagocyte and the particle must adhere to each other, the possibility of which depends largely on the chemical nature of the surface of the particle. In the case of bacteria, if the phagocyte cannot adhere directly, protein components of the blood known as opsonins (e.g., complement and antibodies) form a surface film on bacteria—a process known as opsonization. Phagocytes adhere to the opsonins, and phagocytosis follows. Encapsulated bacteria are ingested with more difficulty. In the absence of specific antibodies that recognize the bacteria, opsonization cannot occur, and the bacteria repel phagocytes.
  60. 60How do natural killer (NK) cells recognize their targets? When they recognize their target, how do they destroy it?Natural killer cells, or NK cells, are a type of cytotoxic lymphocyte critical to the innate immune system. The role NK cells play is analogous to that of cytotoxic T cells in the vertebrate adaptive immune response. NK cells provide rapid responses to virus-infected cells, acting at around 3 days after infection, and respond to tumor formation. Typically, immune cells detect major histocompatibility complex (MHC) presented on infected cell surfaces, triggering cytokine release, causing lysis or apoptosis. NK cells are unique, however, as they have the ability to recognize stressed cells in the absence of antibodies and MHC, allowing for a much faster immune reaction. They were named "natural killers" because of the initial notion that they do not require activation to kill cells that are missing "self" markers of MHC class 1.[1] This role is especially important because harmful cells that are missing MHC I markers cannot be detected and destroyed by other immune cells, such as T lymphocyte cells.
  61. 61Describe how ADCC allows NK cells and eosinophils to destroy their targets.Infected cells are routinely opsonized with antibodies for detection by immune cells. Antibodies that bind to antigens can be recognized by receptors expressed on NK cells, resulting in NK activation, release of cytolytic granules and consequent cell apoptosis. This is a major killing mechanism of some monoclonal antibodies like rituximab (Rituxan), ofatumumab (Azzera), and others. The contribution of antibody-dependent cell-mediated cytotoxicity to tumor cell killing can be measured with a specific test that uses NK-92 that has been transfected with a high-affinity FcR. Results are compared to the "wild type" NK-92 that does not express the FcR.
  62. 62Antigena toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.
  63. 63Immune receptorimmune receptor (or immunologic receptor) is a receptor, usually on a cell membrane, which binds to a substance (for example, a cytokine) and causes a response in the immune system.
  64. 64What are the three types of immune receptor?• Type # 1. Innate (Natural or Nonspecific) Immunity:
    • Type # 2. Acquired (Specific or Adaptive) Immunity:
    • Type # 3. Active and Passive Immunity:
  65. 65Epitopealso known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. For example, the epitope is the specific piece of the antigen to which an antibody binds.
  66. 66Immunogenis an antigen or any substance that may be specifically bound by components of the immune system (antibody, lymphocytes). The term antigen arises from its ability to induce generation of antibodies (antigen = antibody generation). Despite the fact that all antigens are recognized by specific lymphocytes or by antibodies, not every antigen can evoke an immune response. Those antigens that are capable of inducing an immune response are said to be immunogenic and are called immunogens.
    An immunogen is any antigen that is capable of inducing humoral and/or cell-mediated immune response rather than immunological tolerance. This ability is called immunogenicity. Sometimes the term immunogen is used interchangeably with the term antigen. But only an immunogen can evoke an immune response.
  67. 67What are the different types of lymphocytes? Where do they originate and mature.There are three main types known as T cells, B cells, and natural killer cells.
    Both originate from stem cells in the bone marrow and are initially similar in appearance. Some lymphocytes migrate to the thymus, where they mature into T cells; others remain in the bone marrow, where—in humans—they develop into B cells.
  68. 68Primary lymphoid organs(thymus and bone marrow) are the major sites of lymphocyte development (lymphopoiesis).
  69. 69Secondary or peripheral lymphoid organswhich include lymph nodes and the spleen, maintain mature naive lymphocytes and initiate an adaptive immune response. Secondary lymphoid tissue provides the environment for the foreign or altered native molecules (antigens) to interact with the lymphocytes.
  70. 70Why is the secondary immune response faster and stronger than the primary immune response?In a secondary response to the same antigen, memory cells are rapidly activated. This process is quicker and more effective than the primary response.
  71. 71What are the two most important types of T cells?Helper T-cells and Killer T-cells
  72. 72Antigen-presenting cells(APCs) are a heterogeneous group of immune cells that mediate the cellular immune response by processing and presenting antigens for recognition by certain lymphocytes such as T cells. Classical APCs include dendritic cells, macrophages, Langerhans cells and B cells.
  73. 73How is a naïve TH (CD4+) cell activated?Helper T cells become activated when they are presented with peptide antigens by MHC class II molecules, which are expressed on the surface of antigen-presenting cells (APCs). Once activated, they divide rapidly and secrete small proteins called cytokines that regulate or assist in the active immune response.
  74. 74List the 3 signals involved in activation1.) Binding with T-cell TCR and presented peptide, 2.) the CD4 binds to the MHC II portion of the APC. 3.) Recognition of MHC II by CD4.
  75. 75Once activated, what other cells will effector TH cells interact with, and what will their effects be?Interleukin-2, growth factor for t cells, inducing resting cells to enter into cell division for clonal expandion and differentiation
    Cytokines - which will direct immune functions of CD8+ cells, B cells and macrophages.
  76. 76What is the advantage of producing memory cells?They can respond faster by making more and more quickly antibodies with future infection.
  77. 77What are the functions of TH1 and TH2 cells? Why do T cells develop into one or the other?While Th1 cells tend to generate responses against intracellular parasites such as bacteria and viruses, Th2 cells produce immune responses against helminths and other extracellular parasites.
  78. 78What is the difference in the immune response when B cells are activated without T cell help?In this situation activated B cells move to the border of the T cell zone to interact with T cells (Figure 2). CD40 ligand is found on these T helper cells and interacts with CD40 on the B cells to form a stable attraction. Cytokines secreted by T cells encourage proliferation and isotype switching and maintain germinal centre size and longevity. Without these signals the germinal centre response will quickly collapse.
  79. 79Sidephores(Greek: "iron carrier") are small, high-affinity iron-chelating compounds secreted by microorganisms such as bacteria and fungi and serving to transport iron across cell membranes
  80. 80What are other ways in which bacteria obtain iron?Iron is essential for almost all life for processes such as respiration and DNA synthesis. Despite being one of the most abundant elements in the Earth’s crust, the bioavailability of iron in many environments such as the soil or sea is limited by the very low solubility of the Fe3+ ion. This is the predominant state of iron in aqueous, non-acidic, oxygenated environments. It accumulates in common mineral phases such as iron oxides and hydroxides (the minerals that are responsible for red and yellow soil colours) hence cannot be readily used by organisms.[7] Microbes release siderophores to scavenge iron from these mineral phases by formation of soluble Fe3+ complexes that can be taken up by active transport mechanisms. Many siderophores are nonribosomal peptides,[3][8] although several are biosynthesised independently.[9]
  81. 81endotoxinsa toxin that is present inside a bacterial cell and is released when the cell disintegrates. It is sometimes responsible for the characteristic symptoms of a disease, e.g., in botulism.
  82. 82ExotoxinAn exotoxin is a toxin secreted by bacteria. An exotoxin can cause damage to the host by destroying cells or disrupting normal cellular metabolism. They are highly potent and can cause major damage to the host. Exotoxins may be secreted, or, similar to endotoxins, may be released during lysis of the cell.
  83. 83Briefly describe the physiological effects of Shiga toxin, botulinum toxin, and tetanus toxin.ymptoms of Shiga toxin ingestion include abdominal pain as well as watery diarrhea.
    Botulinum toxin (BTX) is a neurotoxic protein produced by the bacterium Clostridium botulinum and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromuscular junction and thus causes flaccid paralysis. Infection with the bacterium causes the disease botulism.
    Tetanus, also called lockjaw, is a serious infection caused by Clostridium tetani. This bacterium produces a toxin that affects the brain and nervous system, leading to stiffness in the muscles. If Clostridium tetani spores are deposited in a wound, the neurotoxin interferes with nerves that control muscle movement.
  84. 84Toxoidsa chemically modified toxin from a pathogenic microorganism, which is no longer toxic but is still antigenic and can be used as a vaccine.
  85. 85Cytolysinsefers to the substance secreted by microorganisms, plants or animals that is specifically toxic to individual cells,[1][2] in many cases causing their dissolution through lysis. Cytolysins that have a specific action for certain cells are named accordingly. For instance, the cytolysins responsible for the destruction of red blood cells, thereby liberating hemoglobins, are named hemolysins, and so on.[3] Cytolysins may be involved in immunity as well as in venoms.
    Hemolysin is also used by certain bacteria, such as Listeria monocytogenes, to disrupt the phagosome membrane of macrophages and escape into the cytoplasm of the cell.
  86. 86Vaccinea substance used to stimulate the production of antibodies and provide immunity against one or several diseases, prepared from the causative agent of a disease, its products, or a synthetic substitute, treated to act as an antigen without inducing the disease.
    A vaccine works by training the immune system to recognize and combat pathogens, either viruses or bacteria. To do this, certain molecules from the pathogen must be introduced into the body to trigger an immune response. These molecules are called antigens, and they are present on all viruses and bacteria.
  87. 87Why do vaccines sometimes fail?1) failure of the vaccine delivery system to provide potent vaccines properly to persons in need; and (2) failure of the immune response, whether due to inadequacies of the vaccine or factors inherent in the host. The first category is by far the most important worldwide. The major factor contributing to failure of the delivery system is failure to vaccinate; in the developing world this is commonly a result of inadequacy of the vaccine supply. Other important factors include barriers to immunizations, improper use of vaccines, vaccine ineffectiveness at the time of use, and factors relating to client attitudes and knowledge. Failure of the immune response may be either primary or secondary (loss of protection after initial effectiveness).
  88. 88Herd immunityIn theory, herd immunity means not everyone in a community needs to be immune to prevent spread of disease. If a high enough proportion of individuals in a population are immune, the majority will protect the few susceptible people because the pathogen is less likely to find a susceptible person. 90-95% of the group needs to be protected for herd immunity to work (in a few cases like polio only 80-85%).

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Microbiology Flashcards on Microbiology Exam 4#, created by Akasya Benge on 30/03/2019.
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