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64 Cards in this Set
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Major Histocompatavility Complex (MHC) antigens
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cell surface proteins which allow an organism's immune system to distinguish between itself and foreign matter
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Name the four major systems of nonspecific defense mechanisms
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Physical barriers (skin, etc.)
Soluble molecules (cytokines, etc.) Phagocytosis Inflammation |
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Name the two major systems of specific defense mechanisms
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Cell-mediated immunity
Antibody-mediated immunity |
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Cytokines
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special protein secreted by cells of the immune system (interferons, interleukins, pyrogens)
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Interferons
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cytokines released in viral infections
effective in inhibiting viral macromolecule production also stimulates other immune response |
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Interleukins
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cytokines secreted by macrophages/lymphocytes
regulates interactions between various parts of immune system |
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Histamine and seratonin
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Released by damaged cells and dilate blood vessels in infected areas
Capillary wall permeability increases leading to tissue oedema and inflammation |
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Increased blood flood to infected areas brings ________, _______ and _______.
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Monocytes, neutrophils and plasma protein gamma globulins (anitbodies)
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Monocytes
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largest leucocytes which phagocytoses pathogens
leave the BVS and enlarge into macrophages |
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Neutrophils
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commonest leucocyte which phagocytoses damaged cells and invading pathogens
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What is thought to be the cause of pyrexia?
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Neutrophils & macrophages releasing endogenous pyrogens (Interleukin-1 & Prostaglandins)
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Pyrogens
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cytokines (proteins) which reset the body's thermostat in the hypothalamus to a higher temperature which affects bacterial metabolism
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Name the two major phagocytotic leucocytes
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monocytes & neutrophils
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Interleukin-1
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pyrogen released by macrophages (monocytes) as part of the inflammatory process, considered to a cause of pyrexia
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Natural killer (NK) cells
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large granular lymphocytes from the bone marrow
release cytokines and perforins (make up 15% of ciculating lymphocytes) |
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What is the role of the non-specific defense mechanisms
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To prevent the spread of infection until the specific mechanisms can come into play
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Cell-Mediated Immunity
What are the major cells involved in the process |
Part of the specific defense mechanism including T-lymphocytes, macrophages, NK cells and dendritic cells
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Describe the development of a T-lymphocyte
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derived from the lymphoblasts in the red bone marrow (pro-lymphoblast)
migrate to the thymus gland to confer immunological competence stored in an inactive state as small lymphocytes in lymph nodes until activated |
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Describe the activation of a T-lymphocyte
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An antigen presenting cell (APC like a macrophage) presents an antigen-MHC complex to a competent lymphocyte with specific receptors which bind to the specific antigen
The activated or sensitized cell increases in size and divides mitotically which differentiate into 4 types |
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What are the 4 types of T-cell subsets of an activated T-lymphocyte?
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Cytotoxic T-cell
Helper T-cell Suppressor T-cell Memory T-cell |
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What do all T-cell subsets do upon reaching the site of infection
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release cytokines and cytotoxins
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Cytotoxic T-cells
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T-cell subset which combines with surface antigens on foreign cells releasing cytokines (perforin-1)
Effective against viruses, bacteria, protozoa, fungi, cancer cells and organ transplants |
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Helper T-cells [two types]
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T-cell subset (60%)
T-helper 1 releases interleukin-2 to stimulate other T-cells T-helper 2 releases interleukin-4 to stimulate proliferation of B-cells |
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Suppressor T-lymphocytes
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T-cell subset which turns off the immune response when fewer antigens are present with suppressor cytokines
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Memory cells
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T-cell subset which remains in lymphatic tissue and is responsible for secondary immune response
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Why is the scondary immune response faster?
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Memory cells, less antigen is required, more antibodies are produced
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Antibody-Mediated Immunity
(humoral immunity) |
Function of the B-lymphocytes
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Describe the development of B-lymphocytes
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Immunological competence develops in the red bone marrow
Each programmed to encode a glycoprotein receptor that binds to a specific antigen Migrate to lyphoid tissues (mainly spleen) separated from T-lymphocytes |
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Describe activation of B-lymphocytes
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APC (like a macrophage/dendritic cell) presents an antigen-MHC complex to a sensitized helper T-cell
B-cell interacts with antigen and degrades it to display the peptide fragments on its surface antibodies Activated helper T-cell binds to the B-cell and releases Interleukin-4 to activate the B-cell Activated B-cells enlarge, divide and differentiate into plasma cells and memory cells |
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Plasma cells
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mature B-lymphocytes with large amounts of rough ER that remain in the lymph nodes and release specific antibodies
these antibodies are transported via lymph and blood to the infected region |
antibodies combine with antigens on the surface of the pathogen to form antigen-antibody complexes
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Antibodies
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highly specific proteins or immunoglobulins
2 identical heavy chains and 2 identical light chains which forms a Y-shape |
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Describe the structure of an antibody
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A Y-shaped molecule with a constant C-region and variable V-region
The V-region acts as a binding site forming the antigen-antibody complex The C-regions interacts with cells of the immune system The Y-shape is made of 2 light and 2 heavy amino acid chains bound with disulfide bonds |
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Name the five classes of antibodies which differ in their C-regions
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IgG, IgA, IgM, IgE, IgD
[GAMED] Ig = immunoglobulin |
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IgG
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makes up 75% of plasma Ig
binds to macrophages, neutrophils part of secondary response activates the complement system by forming antigen-antibody complexes effective against bacteria, viruses crosses placenta |
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IgM
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makes up 10% of plasma Ig
determines blood type part of primary response activates complement system effective against bacteria |
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IgA
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makes up 15% of plasma Ig
found in mucus, saliva, tears and milk effective through viral/bacterial attachment |
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IgD
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receptor on the surface of B-lyphocytes
rarely secreted |
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IgE
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bound to mast cells and basophils
activates allergic/anaphylactic response effective against parasitic worms |
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Basophils
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rarest lecuocyte
contains herapin and histamine associated with mast cells which control allergic reactions |
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True or False
Antibodies destroy antigens |
False
Antibodies don't directly destroy the antigen. They label the antigen for destruction. |
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Name the 3 mechanisms for antibody action
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Direct action
Activate the Complement system Activate the Anaphylactic system |
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List and describe the three components of antibody direct action.
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Agglutination - clumps antigenic agents on cells together
Precipitation - a soluble antigen becomes insoluble and percipitates out Neutralization - the antibodies bind to specific sites on bacterial exotoxins or on viral surface agents |
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Describe the complement system of antibody action
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IgM and IgG form antigen-antibody complexes which activate the first component (C1) of the complement system.
Complement proteins (not antigen specific) destroy the pathogen through lysis, opsonization, chemotaxis, agglutination, virus neutralization or inflammation |
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Membrane-attack complex
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large protein complex made of 5 proteins in the complement system of antibodies which embeds in the plasma membrane of bacteria allowing water to flow inward causing the cell to burst
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Name the 6 processes of complement proteins in the complement system
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Virus neutralization
Opsonization Chemotaxis Agglutination Lysis Inflammation [VOCALI] |
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Describe the anaphylactic system of antibody action
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Activated through IgE
IgE attach to mast cells and basophils in the blood Antigen reacts with exposed IgE on the mast cell by the C-region Mast cell enlarges, bursts and releases histamine which causes local vasodilation/inflammation |
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Describe the progression of Allergic Rhinitis
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Degraded allergen is presented to a T-cell which activates a B-cell to produce pollen-specific IgE which later attach to mast cells.
Pollen combines to IgE on V-region and causes histamine/seratonin release by the mast cell = allergic symptoms Also called "hay fever" |
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Name and describe the primary and secondary bacterial infections
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Primary (localized) infection is via toxigenicity or invasiveness
Secondary infection is invasion of the blood stream |
Toxigenicity = release of toxins
Invasiveness = multiple rapidly at the site of infection Secondary infection sets up new infection sites |
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Describe the structure of the bacterial peptidoglycan layer
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Cellulose-like polysaccharides covalently bound to short peptide chains in layers.
Peptidoglycan strands are linked with transpeptide linkages to provide strength to the cell wall. |
If the peptidoglycan layer is a sandwich, the bread would be the polysachharide layers which contain the short peptide chains.
The transpeptide linkages is what prevents the layers from sliding against each other |
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Distinguish between antibiotics and antimicrobial agents.
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Antibiotics are naturally produced microbial metabolites.
Antimicrobial agents are synthetic products |
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Distinguish between the terms bacteriostatic and bactericidal
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Bacteriostatic = inhibition of growth
Bactericidal = inhibition of survival |
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Recall the four major antibiotic mechanisms of action.
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DNA inhibitors
Protein synthesis inhibition Cell membrane inhibitors Cell wall inhibitors |
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Of the many types of penicillin, state the common trait which they are share.
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Bicyclic ring structure
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65% of all antibiotics are of this type
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Beta-lactans (cell wall inhibitors)
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In penicillin, which of the two rings in the bicyclic ring structure is known as the beta-lactam ring?
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The strained, 4-membered ring
The other rind is a stable, sulfur-containing 5-membered ring |
the bond between the carbonyl and the nitrogen in the beta-lactam ring (cyclic amide) makes the molecule reactive
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Describe the 3D-structure of penicillin
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A well defined, non-planar "half-open book" shape
the rings act as if they are the "covers" of the book |
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What is the target enzyme of Beta-lactams?
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beta-lactams include penicillins and cephalosponis which both target inhibition of transpeptidase to weaken bactertial cell walls
they become osmotically fragile |
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Which beta-lactams are active against gram positive bacteria and which are active against gram negative bacteria?
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Penicillin G is only active on Gram positive bacteria
Cephalosporins are active on both Gram positive and Gram negative bateria |
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Recall the major difference(s) between the bicyclic structure of penicillins and cephalosporins.
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The beta-lactam rings are the same but differ in the adjacent S-containing ring.
Penicillins have a 5-membered S-containing ring whilst Cephalosporins have a 6-membered S-containing ring. |
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What are the two major reasons for the emergence of multi-drug resistant (MDR) pathogens?
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Misuse of antibiotics
Overuse of antibiotics |
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Describe two examples of typical misuse of antibiotics?
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when a course of antibiotics is not finished and strong bacteria re-infect
when antibiotics are used for viral or other inappropriate infections |
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What is the main mechanism of resistance against Beta-lactam antibiotics?
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Bacteria which express beta-lactamases
These hydrolyze penicilin |
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עִם
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With
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com
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Name one method for counteracting bacterial ability to produce beta-lactamases?
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Clavulanic acid blocks active site of beta-lactamase
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