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98 Cards in this Set
- Front
- Back
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What happens when a resting B cell encounters an antigen
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the b cell is stimulated and gives rise to antibody secreting plasma cells
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describe the structure of an antibody
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it is a dimer with variable and constant regions. It has a hinge that allows it to flex around to attach to antigen binding sites.
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what is cdr
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complimentary determining regions or epitope binding sites
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what are the hypervariable regions of an antibody
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the points that actually come in contact with antigens
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what do the Fc portions of antibodies do
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bind to Fc receptors (FcR) on phagocytes and other cells. This anchors the antibody and is crucial for antibody mediated opsonization
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What are the different types of antibody isotypes
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IgG, IgM, IgD, IgA, IgE
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What are the names of the L chain isotypes
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Kappa and lambda
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what is an epitope
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the reion of an antigen that specifically binds to the antibody
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What two conformations can eptiopes come in
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linear such as in bacterial cell walls and conformational such as in proteins
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What is it called when antigens contain more than one epitope
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multivalent
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explain cross reactivity
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the specificity of antibodies can react to the similarity of epitopes. This means that epitopes with similar structures can react to different antibodies
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explain affinity
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the relative strength of a single antibody binding site for antigen
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is affinity qualitative or quantitative
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qualitatiive
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explain aviidity
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the overall strength of the combined binding sites of a given antibody molecule
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is avidity qualitative or quantitative
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auantitative
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what is the effective antibody valence of IgM and why
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up to ten because it can form a pentamer
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what is the effective antibody valence of IgG
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up to two because it forms a dimer in secretions
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what are haptens
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a molecule that cannot provoke an antibody response by itself. It must be coupled to a larger molecule. Haptenylation reactions can occur for both b and t cells
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give an example of a hapten
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penicillin
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how do antibodies result
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recombination of gene segments in B cells
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what enzyme catalyzes b cell gene recombination
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V(DJ) which consists of at least six different proteins
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What are two important components of V DJ
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RAG1 and Rag2
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what would a failure of VDJ lead to
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SCID
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explain the steps of somatic light and heavy chain gene rearrangement
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D and j joined first followed by V
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what is recombinatorial diversity
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diversity due to the ability of the heavy and light chains to join in different ways
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what is junctional diversity
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removal or addition of nucleotides at the joined sections
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what enzyme catalyzes junctional diversity
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TdT or terminal deoxy transferase
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explain somatic hypermutation and where it occurs
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a change in the binding affinity in the hypervariable region and a change in the antibody isotype. Only occurs in b cells, not in t cells
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what is affinity maturation
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a process by hich the affinity of the antibodies for an antigen increase with prolonged or repeated exposure to that antigen
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where does affinity maturation occur
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in the germinal centers
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what are the four main processes that generate antibody diversity
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Multiple V,D,J gene segments (recombinatorial diversity), multiple heavy and light chains (combinatorial diversity), junctional diversity, somatic hypermutation
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how many possible combinations are possible due to antibody diversity
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10^14
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what is the role of alternative mRNA splicing in antibody production
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changing from IgM to IgD and changing from transmembrane IgM to secreted IgM all through changes to mRNA
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what is isotype switching
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a change from one isotype of antibody to the other
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where does isotype switching occur
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at the DNA level
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what mediates isotype switching
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the enzyme AID and cytokines from Th2 cells
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What does isotype switching result in in
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secondary antibody responses
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what are the steps in B cell development
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stem cell, pro, pre, immature b cell
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what happens in pro b cell development
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DJ then VDJ rearrangement in the heavy chains
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what happens in pre b cell development
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VJ rearrangement in the light chains
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what antibody is expressed on the immature B cell and where is it found
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sIgM and its found in the blood
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After entering the lymph node, where do B cells wait for antigens
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primary lymphoid follicles
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what happens when naïve b cells encounter an antigen
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they are activated and differentiate into plasma cells
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where do antigens arrive in the lymph node
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via afferent lymphatics
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what type of antibodies does a naïve B cell express
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IgM and IgD
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where do naïve B cells recognize antigen
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primary lymphoid follicles
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Where does an activated B cell undergo clonal expansion and differentiation
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secondary follicle germinal center
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Where do effector cells secrete their antibodies
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medullary chords, bone marrow, mucosal lamina propria
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where does isotype switching occur
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secondary lymphoid follicle germinal center
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where does affinity maturation occur
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secondary lymphoid follicle germinal center
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where do memory B cells reside
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blood, lymphoid tissues
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What is sIg and how is it activated
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a receptor for antigen and is activated by crosslinking with antigens
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What are the B cell coreceptors
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CD19
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What is a T dependent antigen, where is it found and what does it respond to
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thymus dependant antigen, recognizes proteins, examples include vaccines, diptheria toxin, viral hemagglutin
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what is t independent antigen, what does it recognize and where is it found
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thymus independent antigen, lipids, nucleic acids and polysaccharides. Marginal center. Don’t require T cells. Examples include pneumococcal polysaccharide
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Why is this important to children under two
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they make poor anti-TI responses
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What do TI-1 antigens activate
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all B cells
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What do TI-2 antigens activate
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only mature B cells
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What does class switching require
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T cell help from CD40 and CD40L
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what are the Th cells making to ensure class switching
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cytokines
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Where are plasma cells found
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bone marrow, medullary chords of LN, lamina propria of mucosal tissues
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which cell (resting B or plasma cell) has a high rate of Ig secretion
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plasma cell
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which cell (resting B or plasma cell) can undergo growth, somatic hypermutation, isotype switch
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resting b cell
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what are the effector functions of antibodies
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neutralization, opsonization, complement activation
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where do you find IgG
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blood, tissues
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where do you find IgM
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blood
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where do you find IgA
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body cavities
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Where do you find IgE
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epithelial surfaces, gut, lung
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what Ig can cross the placenta
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IgG
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What Ig is in breat milk
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IgA
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what do maternal antibodies do for the fetus
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protect it until the babys immune system can generate its own antibodies
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What is this process called
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natural passive immunity
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How does IgA cross epithelial surfaces
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through the poly-Ig receptor at the basal lamina and is endocytosed and travels to the surfacewhere the receptor is cleaved and the antibody is now attached to a secretory component
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What cell makes the secretory component
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the epithelial cell
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What protein binds the antibody dimer
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J chain
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What cell makes the J chain
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the B cell
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How do IgG and Iga protect the body
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neutralizing toxins bacteria and viruses
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How do IgG and IgA neutralize toxins
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by binding them and preventing them from attaching to the cell surface
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How do IgG and IgA neutralize viruses
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binding them an preventing their entry into the cell
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how to IgG and IgA neutralize bacteria
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preventing it from binding ot the cell surface
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How are opsonized pathogens engulfed by phagocytes
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The antibodies bind to Fc receptors on the cell surface which activates phagocytosis
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how does IgG enter extracellular spaces
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interactions with a specialized FcRn receptor
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Why does IgE have such a low concentration in the blood
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most are bound to mast cells
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What happens to release granules from mast cells
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multivalent antigens binds and crosslinks IgE
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What is the binding site of IgE to mast cells
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Fc epsilon R+
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What does opsonization of IgE do
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allows Fc epsilon R+ eosinophils to kill multicellular parasites
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The secondary immune reponse is….
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bigger, faster, stronger
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what is the goal of the complement pathway
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to activate C3
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what is complement
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a group of serum proenzymes that are activated by antigen bound immunoglobulin or by membrane components on gram negative bacteria or fungi
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What does C interact with
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antibodies and surface receptors to aid in the elimination of pathogens
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How are classical complement components named
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by placing a C before the number of the component
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Describe the steps of the classical complement pathway
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IgG binds to antigens on bacterial surface, C1q binds to two or more IgG and initiates complement activation. C1q can bind 1 Igm or 2 igg. This binding activates c1r which cleaves c1s. C1s cleaves c4 to c4a and c4b. C4b cleaves c2 forming c4b/c2b complex which cleaves c3 to c3a and c3b. Lots of c3b either binds to c4b/c2b or deposits directly onto the microbial surface. this cleaves c5 into c5a and c5b.
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What do the terminal components of the C pathway do
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polymerize to form pores in membranes to kill pathogens.
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What is the membrane attack complex catalyzed by
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C5b/c6/c7/c8
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What occurs after this complex is catalyzed
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lysis of pathogen
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What inhibits the first stage of the classical c pathway
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C1 inhibitor (C1INH)
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What are the three functions of complement
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Opsonization and phagocytosis, complement mediated cytolysis, stimulation fo inflammatory reactions
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How does complement help in clearing immune complexes
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via binding to C receptors on erytorocytes
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