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31 Cards in this Set
- Front
- Back
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Antibody - general description
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the secreted form of the B cell receptor, also referred to generally as immunoglobulin; this term was originally used to refer to its ability to recognize and bind specific antigens
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Antigen - general description
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the specific molecule(s) of a pathogen to which an immune response is directed; a molecule recognized by antigen receptors of lymphocytes or recognized by antibodies produced by B lymphocytes
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Epitope
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the specific part or feature of an antigen which is recognized by a lymphocyte or antibody
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3 different biochemical roles of immunoglobulins/antibodies
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immediate actions: neutralize toxins, viruses, uptake and clear bacteria
effectors of : classical complement and adaptive immunity effectors autoimmunity: deposition in the joints of patients with rheumatoid arthritis, Lupis |
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clinical importance of immunoglobulins / antibodies
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-target tumor specific molecules in various cancers
-inhibit inflammation in Rheumatoid arthritis- inhibit inflammation -anti myosin in Myocardial infarction -various clinical diagnosis |
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antibodies - source, activation, expansion
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-formed from B cells
-activated by antigen -clonally expand in response to antigen |
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Response to pyogenic infections: who, why
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IgG - recognize capsulated bacteria
IgA- present at mucous membranes |
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3 common capsulated bacteria
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Streptococcus pneumoniae
Streptococcus pyogenes Staphylococcus aureus |
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basic size and structure of immunoglobulin/antibody
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-two heavy chains (50KDa) and two light chains (25KDa)
-two of the same heavy and two of the same light chains -multiple disulfide bonds both intra-chain and inter-chain -variable regions: discrete antigen binding regions in the N terminus |
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fragments from proteolytic clevage of antibody by papain
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Fab - 2 N terminus fragments, weak antigen binding
Fc - 1 complete C terminus fragment proximal to inerchain S-H, crystalizable |
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fragments from proteolytic clevage of antibody by pepsin
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F(ab')2 - one complete N terminus fragment, strong antigen binding
pFc' - one fractured C terminus distal to interchain S-H |
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hypervariable regions - where, how many, aka
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-Fab fragment
-6 total (3 on heavy, 3 on light) -complementarity determining regions (CDRs) |
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CDR3
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contains the most diversity between antibodies
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immunoglobulin multimers - which ones, what need, why
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-IgM pentamer, IgA dimer
-J chain -increases avidity |
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afinity vs. avidity
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strength of antibody binding vs. number of binding sites present
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Enhance phagocytosis (opsonic)
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IgG
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Neutralize toxins
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IgM, IgG, IgA
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Prevent adherence of pathogens
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IgM, IgG, IgA
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Activate classical complement system
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IgM, IgG
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Transport across placenta, through breastmilk
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- IgG, IgA
- IgA |
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Sensitization of mast cells (allergic responses)
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IgE
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Active at mucosal surfaces
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IgG, IgA
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Antigen receptor on naïve B cells
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IgM, IgD
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IgD - role, presence
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-immunoglobulin class with no known function
-present in cartilaginous fish to mammals (not birds) |
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idiotype - definition, use
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-unique combination of epitopes present in the variable region of each unique immunoglobulin
-Antibodies against idiotypes can be used to distinguish antibodies, to clear myeloma |
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private epitopes- definition
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unique epitopes generated by the hypervariable region expressed by a given antibody from a B cell clone
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9 functions of immunoglobulin classes
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Enhance phagocytosis (opsonic)
Neutralize toxins Prevent adherence of pathogens Activate classical complement system Transport across placenta Transport into breast milk Sensitization of mast cells (allergic responses) Active at mucosal surfaces Antigen receptor on naïve B cells |
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Number of variable gene segments in human immunoglobulin loci
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light lambda - 30
light kappa - 40 heavy chain - 40 |
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Number of joining gene segments in human immunoglobulin loci
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light lambda - 4
light kappa - 5 heavy chain - 6 |
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Number of diversity gene segments in human immunoglobulin loci
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light lambda - 0
light kappa - 0 heavy chain - 25 |
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humongous antibody diversity created by
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-combinatorial diversity: germ line genes, chain pairings
-junctional diversity: somatic recombination -somatic hypermutation |
