Lecture Set 6 : Part 3 Flashcards
what is an immunogen?
-any foreign particle that can induce an adaptive immune response
-normally large molecules (proteins, polysaccharides, and some lipids)
what is an antigen?
-any substance that can react with antibodies or receptors on adaptive immune system cells
are all antigens immunogens?
-NO
-all immunogens are antigens, but not all antigens are immunogens (ex: self antigens)
what is the general definition of an antibody?
-protein made by the immune system that can bind to and inactivate foreign antigens
-also called immunoglobulins (Ig)
-antibody is denoted as Ab
what is an epitope?
-also called an antigenic determinant
-the actual part of the antigen that can bind to an antibody
what does the number of epitopes on a single antigen mean?
-the more epitopes on an antigen means the more immunogenic it will be and the more diverse population of antibodies can be generated against it (multiple antibodies for one antigen)
what is the structure of an antibody?
-glycoprotein composed of 4 subunits
-4 subunits = 2 identical heavy chains and 2 identical light chains
-2 identical antigen binding sites (Fab)
-1 Fc site (interacts with other components of the immune system
how many classes of antibodies are there? what are they?
-5 classes
-IgG, IgA, IgM, IgE, IgD
what are the characteristics of the IgG antibody?
-a monomer antibody
-most abundant antibody in blood and tissues (especially in the case of secondary response)
-most important for combating a pathogen
what are the characteristics of the IgM antibody?
-pentamer (5)
-3 sections in the Fc region
-first antibody made when a new antigen is encountered (abundant in primary response)
-excellent at agglutination
-does not leave the blood (not contained within tissues)
what are the characteristics of the IgA antibody?
-dimer (2)
-secreted into saliva, tears, mucous
-helps to protect mucosal surfaces
-important defense against respiratory, reproductive, and digestive tract infections (open to the outside)
-importance within the secondary response (secreted onto mucosa with B-cell activation, NOT in primary response)
-stops infection before it occurs
what are the characteristics of the IgD antibody?
-monomer
-same as a B-cell receptor
-plays a role in activating B cells to respond against an antigen
what are the characteristics of the IgE antibody?
-monomer
-3 sections in the Fc region
-found on the surface of mast cells and basophils
-causes these cells to release granules of histamine
-triggers the allergic response
what are the 5 protective functions of antibodies?
-neutralization
-opsonization
-agglutination
-antibody mediated cytotoxicity
-complement activation
what is neutralization?
-antibodies stick to epitopes on a foreign particle and block attachment sites
-stops the harmful acts from occurring (entrance into host cells)
what is opsonization?
-antibodies stick to a pathogens surface and flag down phagocytes
-phagocyte interacts with the Fc region which causes it to recognize it as a pathogen and then engulfs it
-greatly increases the rate of phagocytosis
what is agglutination?
-antibody can stick to two identical antigens (with sticky ends)
-bridges particles together in clumps so they can be phagocytized more easily
what is antibody mediated cytotoxicity?
-release of granules
-antibody binds to epitopes on the surface of a parasite
-Fc can interact with eosinophils
-eosinophils release enzymes and reactive oxygen intermediates to attack the parasite
what is complement activation?
-antibody binding to a bacterial cell can activate the complement
-complement = a set of proteins in the blood (plasma) that assist other components of the immune system
-complements the function of antibodies
what is the classical pathway of complement activation?
-the complement interacts with the Fc region of an antibody
-activates the complement cascade
what are the major functions of the complement cascade?
-membrane attack complex (MAC)
-opsonization
-enhanced inflammation
what is the membrane attack complex?
-grouping of complement proteins
-poke holes in gram negative bacteria as it has its outer membrane exposed
-dig themselves in to create a pore and release cell contents
what is the purpose of enhanced inflammation?
-attracts phagocytes to the affected area (increases healing)
-innate response NOT adaptive
