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67 Cards in this Set
- Front
- Back
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What is adaptive immunity?
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- Adaptive immunity is a specific attack against specificantigens by a small number of B-cells and T-cells that recognize very specific antigendeterminates.
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What are the features of adaptive immunity? (6) |
- The features of adaptiveimmunity are that the response is: specific, diverse, creates memory of the exposure toantigen, is specialized, self-limiting, and nonreactive to self. |
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Which are theprimary cells involved (2 types)?
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-B-lymphocytes (B-cells) and T-lymphocytes (T-cells)
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What is immunological tolerance and how is itachieved?
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-. Immunological tolerance is theprevention of attack against self-antigens. We currently believe that there may be 2mechanisms by which tolerance is produced: clonal deletion (in which auto-reactive cellsare destroyed) and clonal anergy (in which auto-reactive cells are prevented frominitiating an immune response).
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What is the clonal selection theory?
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- The clonal selectiontheory is that one individual cell is selected, by virtue of its ability to recognize anantigen, to make billions of clones of itself to help the body rid itself of one particularpathogen. When B-cells undergo clonal selection, most clones becomes plasma cellswhich will produce massive amounts of antibody against the particular antigen invadingthe body, after the pathogens have been removed from the body, the plasma cells willundergo apoptosis and die.
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What is a memory cell?
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-Only a very few of the clones becomememory cells, these are long-lived cells (which may live for the rest of our lives) and willimmediately respond to the pathogen with a secondary response, if our bodies areinvaded again.
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A plasma cell?
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-A B-cell which is making massive amounts of antibodies.
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Describe the functions, activation and "life" of B-cells.
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-The sole function of a B-cell is toproduce antibodies, so that pathogens can be "marked" by binding of the antibody to thepathogen, for destruction. A B-cell has the particular antibody that it can produce on itsplasma membrane. If it encounters a pathogen which the antibody binds to, it willbecome activated and start to rapidly divide (clonal expansion), these cells primarilybecome plasma cells which will produce massive amount of antibodies, and a few willbecome memory cells. The fate of these are described above.
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How is a 2nd or subsequent exposure to a particular pathogen different from a 1st exposure?
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- The2nd exposure to a particular pathogen produces an immediate and much stronger immuneresponse, which can very quickly eliminate the pathogen (active immunity).
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Whyis 2nd exposure to a pathogen different?
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-It is different from the initial response, because it is mediated by memory B-cells
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What is active immunity?
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- Active immunity involves activation of B-cells and the production of memory B-cells.
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What is passive immunity?
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-Passive immunity does NOT involve production of memory B-cells, andoccurs when antibodies are given to someone most often via injection or to new borns via breastmilk.
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Example of passive immunity?
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-An example of passive immunity would be administration of antibodies to a person.Because the persons own B-cells were not activiated, no memory B-cells were produced, and theantibodies will only help for the immediate pathogen, subsequent exposures would require moreantibodies to be given.
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Examples of active immunity:
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-When you vaccinate a person, you are givingthem a small amount of a pathogen so that the B-cells can become activated and produce memoryB-cells
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What is an antigen?
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- An antigen is any substance recognized as "non-self" - one criteria ofan antigen is that there seems to be a minimum size requirement, for instance smallforeign peptides (haptens) will not be recognized as "non-self".
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What are antibodies?
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-Antibodies are the glycoproteins produced by B-cells which will mark the pathogen fordestruction
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How many types of antibodies are there?
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-There are 5 major types ofantibodies (IgD, IgM, IgG, IgA, IgE).
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Why do we have different antibodies types?
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- Wehave different types of antibodies because they each have a different function in theimmune system
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How do antibodies help to get rid of a pathogen?
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-They mark thepathogen for 1) phagocytosis or 2) attack by complement proteins
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What are MHC (major histocompatability complex) genes?
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- MHC genes are a group ofgenes that produce 2 different major plasma membrane proteins (MHC class I and MHCclass II)
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What are the functions of MHC genes?
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- These proteins are used to help mark our cells as"self"
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How do MHC genes cause specific responses?
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- MHC class I molecules sample the proteinsthat are being synthesized inside the cell, and present the peptides to T-cells to check tosee that the cells have not been infected. Only certain "antigen presenting cells" haveMHC class II molecules, and these cells can present a foreign peptide to helper T-cells, tocause them to activate other cytotoxic T-cell and B-cells to the presence of a foreignpathogen.
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What are the 2 major types of T-cells?
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- The 2 types of T-cells are "cytotoxic" (or killer) T-cells,and "helper" T-cells
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What are the functions of each T-cell?
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-Cytotoxic T-cells will attack and destroy any cellwhich presents either the wrong MHC class I molecule or an MHC class I molecule with a foreignpeptide in it.
-Helper T-cells will recruit cytotoxic T-cells and B-cells and help to activate onlythose cells which will recognize their particular antigen. |
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How do you tell one T-cell from another?
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-Cytotoxic T-cell have CD8 molecules on their cell surface, and helper T-cells have CD4 on theircells surface.
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How does a T lymphocyte come in contact with an antigen?
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-T cells make contactwith an antigen ONLY when it is presented by the appropriate MHC molecule.
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Do T cells make antibodies?
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-no
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Do T cells form memory cells?
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-yes, as do B cells
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What are the 3 categories of diseases caused by the immune system?
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1. Autoimmune diseases
2.Immune complex diseases 3. Hypersensitivities |
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Briefly describe eachcategory of disease caused by the immune system.
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- Autoimmunediseases fail to tolerate self-antigens and therefore attack the bodies own cells.
-Immune complexdiseases occur because antibodies free in the blood or tissues cause non-specific activation ofcomplement proteins and promote abnormal inflammatory reactions throughout the body. -Hypersensitivity is the clinical term for allergies that are abnormal, massive reactions to allergens. |
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What is immediate and delayed hypersensitivity?
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- Immediatehypersensitivities involve B-cell’s which produce IgE antibodies
-Delayed hypersensitivities do notinvolve B-cells, instead, they involve T-cells that release lymphokines |
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What are characteristics of both immediate and delayed hypersensitivity?
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-Immediate: the IgE antibodies are responsible for intense allergic symptoms including release of histamine, as treatment, antihistamines are used for immediate type hypersensitivities.
-Delayed: corticosteroids are used to prevent the release of lymphokines |
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Innate (non-specific)immunity
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-immunity that comes with the structure of each organism. Does not attack specific pathogens
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Adaptive (specific) immunity
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-acquired ability to defend against specific pathogens by prior exposure to those pathogens
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Immunological competence
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-ability to produce antibodies against non-self antigens while tolerating self-antigens
-occurs 1st month of life |
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Autoantibodies
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-produced after exposure to self-antigens that are normally hidden from blood
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Autoreactive T-cells
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-killer T cells that attack self-antigens
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Clonal deletion theory
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-tolerance occurs b/c T cells that recognize self-antigens are destroyed
-good evidence that this occurs in the Thymus |
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Clonal anergy
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-lymphocytes directed against self-antigens are present throughout life but don't attack self-antigens
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Memory cells
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-what some B cells become after division
-to remember pathogen antigens |
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Plasma cells
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-come from B-cells
-produce about 2000 antibodies/sec that are specific for original antigen -provides active immunity |
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Primary response
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-on 1st exposure to pathogen, there is latency of 5-10 days before specific antibodies are made
-antibody levels plateau after few days & decline after a few weeks |
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Secondary response
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-subsequent exposure to same antigen
-antibody production is much more rapid & sustained |
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Apoptosis
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-organized cell death of leukocytes after infection is mostly cleared out
-returns body back to homeostasis |
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Active immunity
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-development of a secondary response to pathogens
-vaccination |
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Vaccination
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-immunizations induce primary responses by inoculating people w/pathogens whose virulence has been attenuated/destroyed
-cause development of B cell clones that can provide secondary response |
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Passive immunity
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-a transfer of antibodies to a person (by injection or in mother's breast milk)
-provides an immediate response, but b/c the person's B-cells didn't make the antibodies, it will only last a short time -won't prepare the body for a second attack |
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Ab/ immunoglobulins
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-antibodies
-part of gamma globulin class of plasma proteins |
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Heavy chain |
The long chains |
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Light chain |
-shoter chain portion of Y structure |
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Fc fragment
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-the stalk of the Y becomes crystallizable when cleaved
-constant among diff antibodies |
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Fab fragment
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-arms of Y contain antigen-binding fragment
-contains a variable region that confers antibody specificity |
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Complement
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-attracted by antibodies
-form an attack complex, creating large pores in the bacterial membrane -allows for osmotic influx and lysing of bacterial cell |
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Histocompatibility antigens
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-on surface of all body's cells except mature RBCs
-number of proteins, carbs and lipids unique to a individual |
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HLA - human leukocyteAntigens
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-on surface of all body's cells except mature RBCs
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MHC -MajorHistocompatibility complex
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-coded for by group of 4 genes on chromosome 6
-4 genes have multiple alleles creating many possible MHC types -these 4 genes produce 2 cell surface proteins |
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MHC class I
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-made by all cells except RBCs
-bind with protein on killer T cell to examine proteins of cells for foreign cells |
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MHC class II
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-made only by antigen-presenting cells & B cells
-present themselves w/foreign antigen to helper Ts(the only way to activate helper Ts so they can promote B cell activity) -found on the surface of immune cells with which helper T cells interact: dendritic cels, macrophages, B cells -present things being degraded |
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Coreceptors
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-CD8 & MHC Class I
-CD4 & MHC Class II |
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CD8/ Cytotoxic or KillerT-cells
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-CD8 helps the cytotoxic cells recognize foreign proteins in cells by MHC Class I molecules presenting proteins to them
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CD4/ Helper T-cells
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-activated by antigen presentation
-recruit B cells responsive to the antigen -CD4 on helper T cells recognize MHC Class II and screen for foreign substances being degraded in the lysosome |
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virus
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-a pathogen that develops inside host cells
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Autoimmune diseases
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-produced by failure of immune system to recognize & tolerate self-antigens
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Immune complex diseases
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-involve formation of immune complexes that are free and not attached to a cell
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Allergy/hypersensitivity
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-an abnormal immune response to allergens
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Immediate - B-cell - IgE -antihistamine
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-due to abnormal B cell response to allergen; causes effects in secs to mins
-caused by foods, bee stings, pollen -treat with antihistamines |
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Delayed - T-cell -corticosteroids
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-abnormal T cell response that causes symptoms 24-72 hrs after exposure
-treat w/corticosteroids, which prevents release of lymphokines |
