Fundamentals of the Immune System Quiz

Innate immunity refers to natural immunity that is present from birth and is generally non-specific.

Components of innate immunity include physical barriers, inflammatory mediators, complement proteins, acute phase proteins, and immune cells.

Some examples of physical barriers in innate immunity are the skin, mucous membranes, and secretory IgA.

<p>The skin acts as a physical barrier due to its tightly packed, highly keratinized cells.</p> Signup and view all the answers

<p>Some physiological factors that contribute to innate immunity are low pH (5.5), low oxygen tension, and the presence of sebaceous glands that produce hydrophobic oils, lysozymes, and ammonia.</p> Signup and view all the answers

<p>Mucus traps bacteria and contains lysozymes and defensins that directly kill invading pathogens.</p> Signup and view all the answers

<p>Commensal bacteria compete with pathogens for resources and produce fatty acids and bactericidins that stop pathogens from growing.</p> Signup and view all the answers

<p>Cytokines are signaling molecules released by immune cells. They can activate immune cells, induce apoptosis in infected cells, and mediate inflammation.</p> Signup and view all the answers

<p>Macrophages phagocytose bacteria and other pathogens. They have pattern recognition receptors (PRRs) that bind to pathogen-associated molecular patterns (PAMPs), leading to phagocytosis and pathogen destruction.</p> Signup and view all the answers

<p>Mast cells are involved in the immune response against pathogens that are too large for phagocytosis. They release inflammatory mediators and histamines.</p> Signup and view all the answers

<p>The mast cell is stimulated to release pre-formed pro-inflammatory substances such as histamine and tryptase – degranulation. Additionally, the mast cell begins to produce pro-inflammatory substances like histamine, TNF, chemokines, and leukotrienes.</p> Signup and view all the answers

<p>The process is called transendothelial migration, which involves several steps: 1) Loss of intravascular fluid causes slower blood flow, allowing neutrophils to undergo margination. 2) Neutrophils encounter and bind to adhesion molecules expressed by endothelial cells. 3) Neutrophils migrate across the endothelium via diapedesis. 4) Once in the tissues, neutrophils travel to the exact site of injury via chemotaxis.</p> Signup and view all the answers

<p>The three killing mechanisms of neutrophils are: 1) Phagocytosis, which involves the production of reactive oxygen species (ROS). 2) Degranulation, which involves the release of anti-bacterial granules. 3) NETs (neutrophil extracellular traps), which are net-like structures that trap pathogens and lead to phagocytosis.</p> Signup and view all the answers

<p>The modes of ingestion in phagocytosis are: 1) Receptor-mediated endocytosis, where molecules bound to membrane receptors are internalized. 2) Pinocytosis, which is the ingestion of fluid from surrounding cells. 3) Phagocytosis, where bacteria are engulfed by the cell surface.</p> Signup and view all the answers

<p>NK cells are lymphocytes involved in the rejection of tumors and virally infected cells. They respond to levels of MHC class I and kill target cells by degranulation, releasing perforin. NK cells also produce interferon-gamma (IFN𝛾).</p> Signup and view all the answers

<p>Dendritic cells act as a bridge between the innate and acquired immune system. They express antigens on their cell surface and present them to T cells, making them antigen-presenting cells.</p> Signup and view all the answers

<p>Basophils act as effector cells in allergic reactions. Their granules contain substances like histamine.</p> Signup and view all the answers

<p>Eosinophils are associated with allergies.</p> Signup and view all the answers

<p>The three pathways of complement system activation are: 1) Classical pathway, activated by IgM and IgG. 2) MBL pathway. 3) Alternative pathway.</p> Signup and view all the answers

<p>Acute phase proteins are produced by the liver and their plasma concentrations increase or decrease in response to inflammation. Examples include C3, CRP, and MBL, which activate complement pathways.</p> Signup and view all the answers

<ol> <li>PRRs on macrophages bind to PAMPs on pathogen, which signals the formation of the phagocytic cup. 2. Cup extends around the pathogen and pinches off – phagosome. 3. Phagosome fuses with lysosome – phagolysosome. 4. Pathogen killed and contents degraded. 5. Debris released into extracellular fluid. 6. Pathogen-derived peptides expressed on special cell surface receptors (MHC-II). 7. Pro-inflammatory mediators released (TNF⍺) - acute inflammation.</li> </ol> Signup and view all the answers

<p>PRRs on macrophages bind to PAMPs on the pathogen, which signals the formation of the phagocytic cup.</p> Signup and view all the answers

<p>Pro-inflammatory mediators are released (TNF⍺) - acute inflammation.</p> Signup and view all the answers

<p>histamine, tryptase, TNF, chemokines, leukotrienes</p> Signup and view all the answers

<p>They deal with pathogens too large for phagocytosis and release pro-inflammatory substances</p> Signup and view all the answers

<p>Mast cells are associated with allergy</p> Signup and view all the answers

<p>Mast cells play an important role in dealing with dealing with pathogens too large for phagocytosis. When PRRs on mast cell bind to PAMPs on pathogen, the mast cell is stimulated to release pre-formed pro-inflammatory substances such histamine and tryptase – degranulation. As this happens, the mast cell also begins to produce pro-inflammatory substances (histamine, TNF, chemokines, leukotrienes)</p> Signup and view all the answers

<p>The complement system gets activated and creates a cascade of chemical reactions that promotes: 1)Opsonisation of pathogens 2)Direct pathogen killing 3)Acute inflammation 4)Leukocyte recruitment</p> Signup and view all the answers

<p>After C3 convertase is activated by one of the activation pathways:-</p> <ol> <li>C3 is cleaved into the active C3a and C3b</li> <li>C3b can then cleave C5 into C5a and C5b</li> <li>C3b can then amplify the reaction via the alternative pathway, causing more C3 to cleave into C3a and C3b</li> <li>C5b (along with other factors) produces the membrane attack complex, which inserts into cell walls and destroys the cell by letting salt and water in</li> <li>C3a and C5a are responsible for acute inflammation (they are anaphylatoxins)</li> </ol> Signup and view all the answers

<p>Opsonization is an immune process which uses opsonins(extracellular proteins) to tag foreign pathogens for elimination by phagocytes.</p> Signup and view all the answers

<p>C3b plays an important role in the amplification loop of the reaction via the alternative pathway causing more C3 to cleave into C3a and C3b. It also helps in the opsonisation of the pathogens so that they are marked for phagocytosis.</p> Signup and view all the answers