immuno test 2

• Humoral response


  mediated by antibodies (from B cells) to target extracellular pathogens
• Cell-mediated response


  cytotoxic T cells to target virus-infected cells.
• Ig


  immunoglobulin
• affinity


  the binding strength of one antigen binding site
• avidity


  the combined strength of two or more antigen binding site
• crosslinking


  facilitate removal by phagocytic cells such as macrophages
• IgG


  neutrophils, macrophages, facilitates phagocytosis of pathogens
• IgE


  Mast cells, eosinophils, immune response to parasites and allergy
• IgA


  epithelial cells, mucosal immunity secretions
• IgM


  the first antibody to be secreted in an immune response, but is not very efficient
• IgD


  expressed in mature B cells at the same time as IgM, it is mainly exposed as a receptor on the cell surface and very little is secreted as antibody
• TH2 cells


  stimulate immunoglobulin class switching in B cells to produce IgE and recruit mast cells and eosinophils
• allergies

  inappropriate TH2 responses: involve antibodies of the IgE class, mast cells, and eosinophils
• neutralization


  binding on antibodies to bacterial toxins or viruses prevents them from attacking cells by blocking the binding site they normally use to attach to cells
• opsonization


  coating bacteria or other pathogens with proteins such as antibodies facilitates their removal by phagocytic cells such as neutrophils and macrophages
• IgG


  the main antibody isotype used in opsonization
• TH1 cells


  promotes Ig class switching from IgM to IgG
• IgG receptors

  bind to the IgG and tethers the pathogen to the surface of the cells
• clustering of IgG receptors

  activating signals that stimulate phagocytosis and cell activation
• flexible hinge region


  allows antibody to bind with both arms to many different arrangements of antigens on the surface of pathogens
• bigger hinge region


  more flexible and efficient at binding to pathogens, but also becomes more susceptible to proteolytic attack that limits its lifetime
• smaller hinge region


  have a long lifetime because they are less susceptible to proteolytic attack
• complement proteins


  blood proteins that are activated by a proteolytic cascade following antibody binding to antigens on pathogens
• proteolytic conversion of complement C3


  produces C3b which adds another layer of opsonization
• C3b receptors


  combine with Fc receptors for antibodies to enable more efficient phagocytosis of bacteria
• classical pathway


  initiated by binding of complement C1 to antibodies, so it depends on an adaptive immune response
• C1q


  binds to antibody on pathogens
• C1r


  protease that cleaves and activated C1s
• C1s


  protease that cleaves C4 and C2
• formation of C3b

  opsonizes pathogens, the main goal of the complement pathway
• activation of C1


  leads to subsequent activation of C2 and C4 which form the C3 convertase that generates C3b
• C3b


  opsonizes pathogens and also activates the membrane attack complex
• complement C5b-C9


  form a membrane-attack complex that kills bacteria by creating a lytic pore in the membrane
• C3a, C4a, C5a


  stimulate leukocyte recruitment
• C5a


  has the strongest activity
• C4a


  has the weakest activity
• C1


  binds to IgG to IgM antibodies and initiates the complement cascade
• C4b and C2a


  combine to form the C3 convertase
• C3b


  the major opsonin that facilitates phagocytosis
• C3a, C4a, C5a


  functions as important inflammatory mediators in leukocyte recruitment and are referred to as anaphylatoxins