Microbiology Ch 17

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cswett
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78515
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Microbiology Ch 17
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2011-04-10 20:51:22
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Micro Specific Immunity
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Worksheet questions for Ch 17 - Specific Immunity
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  1. What is the 3rd line of defense?
    • Adaptive immunity - acquired
    • - specific response to Ag with a Ab and lymphocytes
  2. What is an Ag?
    substance (protein or polysaccarides) that causes the body to produce Ag or sensitized T cells
  3. Ab
    Immunoglobulin
    • Ab = a protein made in response to an Ag
    • specific Ab that can only combine with that Ag

    Abs are a globulin class of protein (protein with globular form) so Ab are called immunoglobulins (Ig)
  4. 2 branches of the specific immune response?
    • 1. Cell mediated response (T cells)
    • 2. Humoral response or antibody mediated - B cells & plasma cells (Abs)
  5. What is the B lymphocyte
    Plasma cell?
    Memory B cell?
    • B cells = bursa derived (bursa of checken, not human)
    • B cells arise from pluripotent cells that are produced and mature in the red bone marrow

    B cell has specific Ag on it surface - when stimulated by matching Ag - it becomes a plasma cell - makes ↑# Abs (identical to Ab on B cell surface)

    A plasma cell is a mature stimulated B cell that makes Abs

    • Memory cells do not attack invaders - they remain in the system as
    • clones (thousands) after a specific immune response - they speed up
    • immune response is same Ag is encountered again in the future
  6. What is a T cell?
    What does it make?
    • T cell = thymus derived
    • - made in red bone marrow
    • - mature in thymus (lymph tissue

    Each has specific T cell receptor that binds to specific Ag - when Ag binds T cell is stimulated and produces cytokins → immune repsonse
  7. What is a hapten?
    Hapten = an small Ag molecule (too small to register respone) that contains an epitope - needs to be combined with a carrier protein to cause an immune response

    2nd encounter - hapten alone will trigger immune response
  8. 4 Types of T cells
    • a. Cytotoxic T cells - CD8 (co-receptor)
    • - activated by cytokins - cause apoptosis

    • b. Helper T cells - CD4 (co-receptor)
    • - release cytokins → activate dendritic cells (APCs), macrophages, cytotoxic T cells, B cells (plasma cells)

    • c. Memory T cells - CD4 & CD8 (co-receptors)
    • -
    • d. Regulatory T cells - turn off specific immune response
  9. What is an epitope?
    Epitope = the part of an Ag that binds to the Ab and starts the immune response - also called an antigenic determinant
  10. Step in cell mediated immunity -
    Exogenous and Endogenous processing
    • CD4 T cells: -Exogenous Processing (MCH II/ Ag)
    • 1. APC presents Ag to CD4 lymphocyte - Ag binds at TCR (T cell receptor) and CD4 is the coreceptor
    • 2. Costimulant (such as IL-2) causes cell to become activated
    • 3. CD4 T cells make active helper T cells - (they secrete cytokins (IL-2) and memory T cells - not active until next contact with Ag

    • CD8 T cell - Endogenous processing (MCH I/ Ag)
    • 1. APC presents Ag - Binds at TCR and CD8 is the coreceptor
    • 2. Costimulator (possibly IL-2 secreted by activated CD4 cells) causes cell to be activated
    • 3. Cell makes clones of active cytotoxic T cells - (attack invaders) and memory cytotoxic T cells - (can quickly activate and make active and
    • memory cytotoxic T cells at next meeting of Ab)
  11. Ab diagram
    What binds to the heavy chains?
    What is the valence?
    • Complement and macrophages bind to the heavy chains on compliment.
    • Ab monomer has a valence of 2

  12. What are the 5 classes of Abs?
    % = % of all Abs in serum

    • 1. IgG (80%) - most abundant in blood - able to leave blood & migrate into tissue during immune response
    • - monomer
    • -triggers compliment when bound to Ag
    • - increases phagocytosis (opsonization)
    • - kills viruses & toxins
    • - crosses placenta - innate immunity in fetus

    • 2. IgM (7%) - large pentamer (M=macro)
    • -1st Ab involved in immune respone -short life
    • - triggers compliment
    • -causes aggregation (valence 10)
    • - serves as Ag receptor on surface of B cells - also found in blood in lymph

    • 3. IgA (10%) - most abundant in body (not serum)
    • - in secreations - mucous membranes - salvia, mucus, tears, milk
    • - blocks adherance to membranes
    • - dimer

    4. IgD (.2%) - monomer - unknown function

    • 5. IgE (.002%) - monomer -
    • -serves as Ab receptor on Mast cells, basophils, eosinophils
    • - particiapes in allergic reaction - in presence of allergen IgE stimulates the mast cell to release histamine
    • - large #s during allergic reacion
    • - involved in extracellular killing of large parasites
  13. Which Ab crosses the placenta?
    IgG
  14. Which Ab is a pentamer, 1st to respond to an Ag, and cannot fit out of a blood vessel?
    IgM
  15. Which Ab is on the surface of a B cell?
    IgM, IgD
  16. Where is IgA found?
    In secreations - saliva, milk, tears, mucus
  17. Do you have a lot of IgE in your serum? When do you?
    What cells binds it? What does this cell release?
    • No unless having an allergic reaction - then lots
    • Bound to Mast cells, basophuils, eosinophils that relase histomine in presence of allergen
  18. What is an Antibody Reaction?
    What are the responses?
    • When an Ab/ Ag complex form Ab tabs microbe for death by:
    • 1. aggluatination - clumping
    • 2. opsonization - ↑ phagocytosis
    • 3. activates compliment
    • 4. cell mediated death (eosinophils → lytic enzymes)
    • 5. neutralization of microbe - cant adhere
  19. Is IgA a monomer?
    No it is a dimer
  20. What 3 cells are capable of phagocytosis?
    • 1. macrophages (A monocyte matures into a macrophage in tissue (not in blood stream)
    • 2. neutrophils (PMNs)
    • 3 .APCs - dendritic cells
  21. What is microbe agglutination?
    In agglutination (also called aggregation) Ab cause Ag to clump together. IgM is very good at this becuase it has a valence of 10
  22. What is the B cell response?
    T-independent & T-dependent responses
    • Ab mediated immune response occurs in the lymphoid tissue. T dependent Ags:
    • 1. B cell eats Ag and is broken down into peptide fragments (combined with MHC-II) and moved to B cell plasma membrane
    • 2. Helper T cell binds to B cell and costimulates - B cell divides into: Plasma cells & Memory B cells

    • a. Specific B cell receptor (BCR) binds with an Ag
    • b. The cell is now actived and undergoes clonal selection - plasma cells that secrete Ab and memory B cells for next encounter
    • c. Plasma cells release thousands of Abs that travel in the lymph to site of infections

    • T-independent Ags:
    • Ags stimulate B cell directly-
    • - provokes a weaker immune response
    • - response is primarily IgM
    • - no B membory cells are generated
  23. What is self tolerance?
    Body dosent make Abs against itself

    • all body cells (except RBCs) are tagged with MHC Ags
    • -also called HLA Ags - Human leukocyte Ags
    • - your body ignores there Ags

    • After organ transplants the patient must take medication that inhibits
    • immune response becuase the Ag on the new organ are foreign - the body
    • will try to attack it. This is also a factor in autoimmune diseases
    • where lymphocytes attack the bodys cells. However, it is not an issue
    • in blood transfusion becuase the RBC do not carry MHC Ags - they only
    • carry blood type Ags
  24. What is clonal selcetion?
    Clonal Deletion?
    Clonal selection = creating memory cells that are responsible for an enhanced secondary response to an Ag

    Clonal deletion = removing all clones of B and T cells that are capable of damaging "self Ags"

    Autoimmune diseases are those where cells arise that do not recogine "self Ags" are are able to damage body cells.
  25. What is a dendritic cell?
    • A dendritic cell is a type of APC -it is nonspecific
    • It is an agranulocyte derived from a moncyte
    • -primary APC - engulf invader and take to T cells in the lymph
  26. What do regulatory T cells do?
    • Supress and inhibit other T cells
    • - combat autoimmune disease by inhibiting T cells that escape deletion in the thymus
    • - turn cell mediated immune reactions off using cytokins
  27. APC
    • APC - Antigen Presenting Cell
    • Dendritic Cells & Macrophages

    • 1. They eat (phagocytosis) invaders
    • 2. Attach a peptide fragment to their plasma membrane via MHC (major histocompatibility complex)
    • 3. Travel to lymphatic tissue to present the antigen to T cells
  28. What is a natural killer cell?
    • Natural killer cells (NK) are nonspecific lymphocytes -
    • they can also attack parasite and tumors
  29. How do cytotoxic T cells kill mocrobes?
    Cytotoxic T cells leave lymphatic tissue and travel to infection - bind to cells with specific microbial Ags

    • kills cell by one of several options:
    • 1. can release granzymes - protein -digesting enzyme that trigger apoptosis (progranned cell death)
    • 2. can release Perforin and granulysin
    • - perforn makes hole in cell membrane (cell lysis) and granulysin enters cell through hole and kills microbe by creating holes in it cell membrane.
    • 3. can release lymphotixin - activates enzymes in the target cell that cause the cells DNA to fragment (cell dies)
  30. What are the functions of cytokins
    • Proteins- they mediate immune responses - produced by all cells of immune system in response to a stimulus
    • -can stimulate or inhibit it
    • -activate macrophages
    • - transform B to plasma cells
    • - transform B and T to memory cells

    In Humoral response (B cell - Ab) - Helper T cell binds to B cell and releases cytokins to make B cell proliferate faster → plasma cells + memory B

    • Examples:
    • IL (interleukins), interferons, TNF tumor necrosis factor
  31. WBCs
  32. What 2 things can activate a macrophage?
    • foreign Ags
    • cytokins
  33. What is ADCC?
    Antibody-dependent cell-mediated cytotoxicity

    • specific reaction Ab/Ag
    • Extracellular killing - invaders that are too large to be phagotized - parasites

    • 1. Parasite is coated with Ab
    • 2. Macrophages attach to C regions of IgE & IgE can bind to eosinophil cell membrane
    • Ag/IgE binding → enzymes released that digest parasite
  34. Primary & Seconday immune response
    Ab titer
    • Ab titer - relative amt of Ab in the serum
    • IgM - first Ab produced
    • IgG - second Ab produced
  35. Natural passive immunity
    Natrual active immunity
    Artificial active immunity
    Artificial Passive immunity
    • Natural passive immunity - mother to fetus
    • Natrual active immunity - infection Ab/Ag reaction
    • Artificial active immunity - vaccination - inject Ag
    • Artificial Passive immunity - inject Ab
  36. Antiserum
    • Blood serum with Ab against a certain Ags
    • Injection can give immediate passive protection against the disease (that produced the Ags) - it does not last long (about 3 weeks)

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