B cell S3M1

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B cell S3M1
2011-09-10 16:21:40
Ross S3M1

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  1. Most B cells require stimulation from
    T cells
  2. During opsonization, what region of the antibody is recognized by the macrophage
    The Fc region
  3. What kind of antigens do B cells recognize
    • Proteins
    • Carbohydrates
    • Lipids
    • Nucleic acids
  4. B cells undergo differentiation where
    In the bone marrow where they acquire functional competence
  5. Stem cells (CLP) commit to B cell differentiation via
    Cytokines released from bone marrow stromal cells (this happens in the absence of an antigen)
  6. What are the stages of B cell differentiation
    • Stem cell
    • Early pro-B cell
    • Late pro-B cell
    • Pre-B cell
    • Immature B cell
    • Mature B cell
  7. How can one recognize an early Pro-B cell
    CD19 presence
  8. What rearrangement happens in the early Pro-B stage
    Rearrangement of the heavy chain namely D and J gene segments are joined
  9. What rearrangement happens in the late Pro-B cell stage
    Joining of the V segment to the rearranged DJ segment
  10. Rearrangment of the B cell immunoglobulins occurs via what genes
    • RAG-1 & 2 (Splice)
    • TdT (Inserts nucleotides)
  11. How many attempts are possible for the B cell heavy chain to create a viable chain
  12. RAG 1 and 2 are most active at what B cell stages
    • Early and late pro-B cell
    • Small Pre-B cell to Immature B cell
  13. TdT is most active during what stages of the B cell development
    Pro-B to Pre-B cell development
  14. What is the purpose of the surrogate light chain
    • This is to test the heavy chain to verify that it can combine with a light chain
    • When attached it is considered the Pre-B cell receptor
  15. What two proteins make up the surrogate light chain
    VpreB and lambda 5
  16. Allelic exclusion
    Successful assembly of the Pre-B cell receptor stops RAG genes preventing the rearrangement of the second heavy chain locus
  17. How many functional immunoglobulin genes are expressed on one B cell
    Only one
  18. Light chains of immunoglobulins have how many attempts possible to make a viable receptor
  19. What would happen if allelic exclusion doesn't function
    B cell would express multiple rearranged immunoglobulin genes and would result in low affinity for any antigen
  20. What is central tolerance
    Making sure the B cell recognizes self cells as safe
  21. What are the three options of the B cell fate while undergoing Central tolerance
    • No self reaction - Migrate to periphery for further maturation
    • Multivalent self antigen - Apoptosis
    • Soluble self antigen - Anergic B cell formed (quiescent)
  22. What is receptor editing
    Immature B cells that react with self can undergo one more attempt to re-arrange an affective light chain
  23. The second chance receptor editing only happens wih
    Light chain
  24. Peripheral tolerance
    • This is the last check to ensure that the B-cell is not reactive to self antigens
    • This happens in the periphery because not all antigens are present in the bone marrow
  25. When a B cell exits the secondary lymphoid tissue what form is it in
    Mature B cell
  26. Where do the immature B cells receive the signal to survive and mature
    Secondary lymphoid tissue (the signals are cytokines)
  27. What happens to a naive mature B cell causing it to undergo changes in gene expression
    It binds to an antigen causing changes in gene expression of the B cell
  28. What are the B cell co-receptors
    • CD19
    • CD21
    • CD81
    • Ig-alpha and Ig-beta
  29. CD21 is also known as what, and has what function
    • Complement receptor 2 (CR2)
    • It recognizes breakdown products of C3d fragments that bind the B cell to the surface of a pathogen
  30. What cytokines are involved in B cell activation
    • IL-1
    • IL-4
    • IL-6
    • IFN
  31. Antibody response to most antigens by the B cells requires help from
    CD4 T cells
  32. IL-5 and IL-6 have what effect on the B cells
    Drive differentiation of B cells to plasma cells
  33. When a B cell becomes a Plasma cell what functions does it loose, what does it gain
    • Loses surface IgM and MHC class II expression
    • Gains the ability to synthesize and secrete many IgM
  34. CD40 Is found on what cells and responds to what
    Found on B cells and responds to the expression of CD40L on T cells
  35. Plasma cells contain many of what organelle and why
    ER to make lots of proteins
  36. What specialized methods do B cells have to improve their antibody molecules
    • Somatic hypermutation
    • Affinity maturation
    • Isotype (class) switching
  37. Where do the Post activation B cells undergo antibody improvement
    In the germinal center of lymph nodes
  38. Isotype switching involves what portion of the Immunoglobulin
    Only the constant region, never the variable region
  39. How do B cells respond to the combination of CD40L and IL-4 expressed on the T cell
    • B cells begin to divide
    • Somatic Hypermutation begins
    • Affinity maturation begins
    • Isotype switching begins
  40. What is somatic hypermutation
    Random addition of single nucleotide substitutions at a high rate on the variable region of the heavy and light chains
  41. What occurs to a B cell when it encounters its antigen
    • Engulfs it and digests it
    • Displays the antigen fragments on MHC
    • This attracts mature T cells
    • Cytokines (IL-5 & IL-6) secreted by the T cell causes the B cell to divide and differentiate into plasma cells
    • Plasma cell secretes antibody against anitgen
  42. Thymus independent antigens
    Antigens that can trigger a response to B cells without the help of a T cell
  43. What do B cells not undergo when activated by Thymus-independent antigens
    Affinity maturation and class switching and therefore only produces IgM antibodies
  44. What B cells are found in larger quantities in neonates
    B-1 B cells
  45. B-1 cells differ how
    • They express CD5+/CD5- and more IgM then IgD
    • They preferentially respond to T independent antigens
    • Can often cross with multiple antigens
    • Reactive to bacterial antigens
  46. What is the receptor for Epstein Bar Virus (EBV)
  47. B-2 are considered conventional B cells why
    • They are reactive to T cell dependent antigens
    • They are mature B cells
    • They have a more diverse effects then B-1
  48. B-2 cells have more of what antibody on their surface
    More IgD then IgM
  49. IgM antibodies are specialized for what responses
    • Classical complement pathway
    • Great for elimination of pathogens from the blood stream
  50. IgA antibodies are very important for
    Neutralizing antigens and provide protection against pathogens commonly found in the GI tract and mucosal surfaces
  51. What induce B cells to switch isotopes
    Cytokines produced by activated CD4 T cells (IL-4)
  52. IgD is only expressed where
    On the surface of Naive B cells
  53. IgA is prevalent in what
    Secretions (tears, saliva, mucous)
  54. What is the only antibody that crosses the placenta
  55. What antibody sensitizes Mast cells