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50 Cards in this Set
- Front
- Back
Humoral Immunity
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Host defense mediated by sereted antibodies
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Humoral immunity main function is
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preventing infection
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what are the 5 different classes of antibodies
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IgG IgA IgM IgD and IgE
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the heavy and light chains are held together by what type of bonds?
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noncovalent and disulfide bonds
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Each Ig class is represented by a different
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heavy chain
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Proteolytic cleavage by papin produces
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2 Fab
1 Fc |
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Fab
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binds to antigen
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Fc
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-initiated complement activity
- binds to cell receptors nonimmunologically |
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Thymus-independent antigens
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able to activate naive Bcells without the help of CD4 T helper cells
(mostly bacterial pathogens) |
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Thymus-dependent antigens
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activates B cells in the secondary lymphoid tissues and involves, Bcells, Specific antigenand helper CD4 T cell(main difference)
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Thymus-dependent antigens are
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processed and presented by APCs
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What are two examples of APC
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Dendritic Cells or Macrophages
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antigen-specific CD4 T cells are activated to become
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effector T helper cells
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T helper cells interact with
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dendritic cells
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dendritic cells present specfic antigen to
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MHC II class receptors on Bcells
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clonal selection
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some B-cells will differentiate into antibodu-secreting plasma cells or become memory Bcells
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B cells are intially programmed to produce ___ antibodies
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IgM
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________ enables B-cells to swtich to the production of a different class of antibody
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effector T-cell
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B cells activated by helper Tcells form a focus of dividing
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B lymphoblasts
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Germinal centers are specialized microenvironment for
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- B cell proliferation
- Somatic Hypermutation - Selection for antigen binding |
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Centroblasts
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-Bcells maturing in germinal centers
-Somatic hypermutation |
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Centroblasts mature into
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Centrocytes
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Centrocytes
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- Nondividing
- Mutated surface immunoglobulin (affinity for its specific anitgen can be higher, lower or the same) |
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somatic hypermutation occures in
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rapidly proliferating germinal center Bcells
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Effector functions of antibodies
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1. Neutralization
2. Opsonization 3. Complement activation |
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Neutralization
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antibody blocks binding sites of the anigen so they cant be taken up by the cell or in bacteria block against adhesin block colonization and uptake
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opsonization
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Fc help to enhance phagocytosis of the bacterium
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Fc receptors are located on what cell types
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macrophages
neutrophils eosinophils |
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Antibody dependent cell-mediated cytotoxicity
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Fc receptors on NK form crosslink and signals the NK to kill the cell
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All 3 pathways of complement cascade lead to
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cleavage of C3 into C3b and C3a
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C3b binds to
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pathogens surface (complement fixation)
-Aids in opsonization |
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C3a attracts
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inflammatory cells
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C2a binds to
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C4b
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classical pathway of complement cascade is initiated by
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antigen-antibody complexes
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C5b, C6, C7 C8 combine to form a complex which initiated the
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polymerization of C9 to form a MAC
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MAC forms a
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pore in the membrane causing the lysis of the cell
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Isotype Switching
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diversifies functional properties of hte antibody Fc region
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IgD is found on
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mature naive B-cell membrane
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first antibody produced in an immune response
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IgM
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IgM is present in
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blood nad extracellular fluids
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IgM is secreted as a
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pentamer
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phagocytic cells do not have receptors for what antibody Fc receptors
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IgM
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second antibody produced in an immune response
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IgG
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IgG
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-Dominant blood borne antibody
-Able to cross the placental barrier (provides passive immunity for baby) |
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Circulating IgM and IgG prevent
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septicemia
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IgA is produced in
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MALT (mucosal-associated lyphoid tissues) - mucosal epithelium and in breast milk which provides passive immunity to baby
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IgA protect
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surfaces of the epithelial that are in direct contact with the external environment
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IgE binds to Fc receptors of
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mast cells
basophils eosinophils |
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granules in the cytoplasm of the mast cell contain
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histamine
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Antigen binding of FceRI receptors result in
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immediate effector function
(cell proliferation, differentiation not required) |