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88 Cards in this Set
- Front
- Back
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What is the first barrier of defense?
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The skin
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Why are the gastrointestinal, urogentital tracts and the lungs an ideal environment for bacteria to grow?
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They are warm (37 degrees), humid (bathed in fluid) and have an ideal neutral pH (between 7 and 7.4)
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How can bacteria enter through the skin?
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Through pores or hair follicles
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What are typical places to contract infection?
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The mouth, digestive and urogenital tract, and the lungs
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Where are microflora present?
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Mouth, anus, large intestine
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How do microflora defend us?
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They compete for space in the areas that pathogenic bacteria could infect, thus making it more difficult for the pathogenic bacteria to enter and cause infection
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What is the pH of the skin?
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5.0
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How do the keratinized cells protect us?
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The keratin is hard to degrade. Also, the dead cells slough off and thus adherent bacteria will also fall off
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Which molecules protect the hair follicles and sebaceous glands from bacteria?
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Toxic lipids and lysozyme
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Which species is part of the skin flora?
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Staphylococcus epidermis
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What are the phagocytic cells at the skin surface?
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Langerhans
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What type of epithelium is found in the intestinal tract?
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Simple epithelial cells
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Why is the skin and mouth more resistant to bacterial invasion than the intestinal tract?
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The skin and mouth have stratified epithelium, multiple layers, and are thus harder to breach while the simple layer of epithelial cells in the intestine is easier to breach
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What does the movement of cillia llow?
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The mucous with trapped bacteria to be expelled
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What are the two ways the eyes protect against infection?
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Blinking and tears
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How does blinking act as a barrier against infection?
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Blinking gets rid of any bacteria that are at the surface of the eyes
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How do tears help to get rid of bacteria in the eye?
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They contain lysozyme, IgA and lactoferrin
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What are the defense mechanisms in the nasopharynx?
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Resident microflora, secretions and nose hairs
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What is the microflora in the nasopharynx typically composed of?
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Gram-positive cocci
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What are the barriers in the lung that protect against infection?
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-Curved design of the lung
-Macrophages -Ciliated cells |
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How does the curved design of the lung protect against infection?
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When you inhale, the air creates turbulence, detaching any bacteria or foreign substances in the lungs which can then be gotten rid of by coughing or sneezing
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What are the barriers in the mouth?
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-Lysozyme, IgA, and lactoferrin in the saliva
-Microflora |
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What are the barriers in the stomach?
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Low pH, and proteolytic enzymes
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What is a species of bacteria that is capable of living in the stomach?
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H. pylori
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How is the small intestine protected?
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Fast flow, mucus and sloughing cells
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What is the main way that the large intestine is protected?
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Abundant microflora compete with bacteria that reach the area
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Where are M cells found?
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Peyer's patches in the gut lumen
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What does the M cell do?
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The specialized M cell takes up antigens from destroyed pathogens, and then dendritic cells can process and present antigen to lymphocytes to allow the infection to be controlled
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Are there microflora in the bladder?
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NO
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How is the bladder protected?
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Flushing action of urine, low pH, physical barrier of urethra
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How is the vagina/cervix protected?
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low Ph and resident microflora
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What are the resident microflora composed of in the vagina/cervix?
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Gram positive and negative species
Lactobacllus (creates the low pH) |
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How are the uterus and fallopian tubes protected?
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Mucous plug at cervical opening protects from infection
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What is mucous produced by?
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Goblet cells
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What are some physical characteristics of mucous?
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Viscous and slimy
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What does the presence of mucous in urine indicate?
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An infection
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How does the mucous work to prevent penetration by bacteria?
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It traps bacteria at the surface of epithelial cells, preventing the attachment. Cilia in the lungs beat back and forth, allowing the mucous coated pathogens to be expelled.
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What does lysozyme do?
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Digests peptidoglycan
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What does lactoferrin do?
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Sequesters iron
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How does sequestering iron prevent bacterial infection?
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It is an essential nutrient for bacteria and thus sequestering iron will block bacterial growth
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What is the N terminal portion of lactoferrin?
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Lactoferricin
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What does lactoferricin do?
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Binds to bacterial LPS to further protect the host
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Where are defensins produced?
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Mouth, tongue and crypts
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Which cells produce defensins in the gut?
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Paneth cells
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How is human defensin 5 activated?
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Upon detection of bacteria, trypsin (a zymogen) will clip pro-human defensin 5, yielding an activated human defensin 5
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How are defensins designed?
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THey have an amphipathic design (part hydrophillic/part hydrophobic)
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Why dont defensins interact with our cells?
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Our cells have neutral plasma membranes. Converesely, bacterial cells are negatively charged and will therefore exhibit a strong electrostatic attraction to the positively charged defensin
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What does the specific/nonspecific lymphoid mucosal defense involve?
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Antibodies, phagocytic cells, cytotoxic cells, mast cells and other PMNs
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How do lymphoid cells act in the first line of defense?
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Mature lymphoid cells migrate in the blood in a resting state. During infection, they are activated and leak to the lymphatics or transmigrate to the tissue.
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How are contents dumped back into the bloodstream from the lymphatics?
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The thoracic duct
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Which bacterial species can survive killing at the nodes?
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Yersinia pestis
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What are the main lymph nodes in the body?
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Mediastinal, Mesenteric and Peyer's patches
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Where are B cells located in the lymph node?
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Primary lymphoid follicles and secondary lymphoid follicles with germinal centers
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Where are T cells located in the lymph node?
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The paracortical area
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Where are macrophages and plasma cells located in the lymph node?
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Medullary cord
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What are addressins?
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Molecules that help immune cells recognize the site of infection
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How do adhesion molecules help an immune cell to reach the site of infection?
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Adhesion molecules are upregualted in response to cytokines. THey attach to receptors on the endothelial cells, causing the cell to roll along until it reaches the site of infection
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What are some molecules that can regulate chemoattractants, addressins and adhesion molecules?
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Cytokines such as TNF-alpha, IL-1Beta and MRP (myeloid related protein)
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What are the two types of phagocytic cells?
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PMNs and Professional APCS
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What is an example of a motile macrophage?
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Alveolar macrophage
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What is an example of a stationary macrophage?
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Kupffer cells (in the liver)
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What are two examples of reactive oxygen species?
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Superoxide and hydrogen peroxide
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What are ROS produced by?
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NADPH oxidase
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What are NETs?
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Neutrophil Extracellular Traps
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What is the function of NETs?
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Trap, degrade bacterial virulence factors and kill bacteria
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What are NETs composed of?
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Extracellular fiber matrix made from granular proteins and chromatin
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What are examples of proteases in the phagosome?
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Elastase and cathepsin G
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What is an example of a bacterium that can modify the surrounding pH to survive in the phagolysosome?
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Mycobacterium tuberculosis
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What is NO produced by?
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Monocytes, macrophages and neutrophils
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What are the two types of nitric oxide synthesase (NOS)?
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Inducible and constitutive
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What can stimulate macrophages to produce iNOS?
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Gamma-interferon and TNF-alpha
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How does iNOS work to produce NO?
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It converts L-arginine to L-citrulline and nitric oxide
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What happens when NO combiens with superoxide?
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Peroxynitrate
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What is iNOS expressed by?
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Macrophages, microglia, neutrophils, eosinophils, fibroblasts, endothelial cells, epithelial cells a astroglia
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How does iNOS work?
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As a homodimer
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How does iNOS dimerize?
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Under the the action of calmodulin and the incorporation of heme
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How is consitutive NOS turned on?
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An increase in Ca++
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What is iNOS expression regulated by?
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IL-1, TNF, and IFN
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What decreases the signalling to express iNOS?
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IL-10, TGF-beta and iL-4
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What are the different dependencies on iNOS?
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-Dispensable to control infection
-Essential for control -Contributes to control -Detrimental to host |
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What is an example of a bacteria that favors NO production?
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Ex: S. pneumoniae -> NO kills lung cells which permits the bacteria to invade and travel to the blood
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When can collateral damage due to infection control occur?
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IN an immunosuppressed state or during infection by a particularly pathogenic bacteria
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What are two molecules cytotoxic cells produce to kill infected cells?
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Perforins and grazymes
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What are examples of cytotoxic cells?
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Natural killer (NK)
Cytotoxic T-cells |
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What do perforins do?
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Form channels in the bactrial membrane
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What do granzymes do?
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Induce apoptosis of the target cell
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What are two ways perforin and granzyme work together to kill the infected host cell?
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1) Perforin creates pores which granzyme can travel through and induce target cell death
2) Granzyme can interact with a receptor, and both granzyme and perforin will be taken up in vesicles and work together at the phagosome level |
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How can pathogenic bacteria induce damage?
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Directly or indirectly (due to methods needed by the host to control infection)
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