Card Set Information

2010-03-31 17:12:11
2 2_Immune_B cells

B-cell maturation and activation
Show Answers:

  1. Q: What are two methods of diversity for the protein sequence of an Ig molecule?
    A: Somatic Mutation; where mutations in the coding sequence are inserted during B cell maturation. Recombination; there are many coding sequences that encode the variable region of the Ig protein.
  2. Q: How many different isotypes can one B cell make.
    A: ONE!!! A single B cell makes a single heavy chain protein. (monoclonal)
  3. Q: Describe the concept of monoclonal (this was bold and underlined so know this!!!)
    A: For any given B cell, its product is a single Ig protein made up to two identical light and two identical heavy chain proteins.
  4. Q: What is VDJ anyway?
    A: Variable, Diversity, and Junctional coding sequences in the gene. The sequences between these are removed to have one V, one D, and one J come together to form a single VDJ coding sequence.
  5. Q: Which chain is made first, heavy or light?
    A: Heavy
  6. Q: What regions do light chains have, (only two).
    A: Variable and joining, NO DIVERSITY.
  7. Q: What enzyme inserts DNA sequences at the junctions of V, D, and J regions?
    A: Terminal Transferase. (adds single nucleotides generating more diversity).
  8. Q: What is class switching?
    A: generating different isotypes by altering the HEAVY CHAIN ONLY.
  9. Q: In what order are the different isotypes of Ig chains made?
    A: IgM, IgD, IgG, IgA, IgE
  10. Q: How does antigen specificity change during class switching?
  11. Q: How many chances does a B cell have to obtain productive VDJ maturation?
    A: 2 chances in the heavy chain and four chances in the light chain (kappa, and lambda).
  12. Q: What is the Rag enzyme used for?
    A: it facilitates VDJ rearrangement by recognizing the RSS (recombination signal sequence).
  13. Q: List 5 more stages of maturation for the lymphocyte beginning with the stem cell.
    A: pro-lymphocyte, pre-lymphocyte, immature lymphocyte, mature lymphocyte, differentiated effector lymphocyte
  14. Q: Which stage of lymphocyte maturation takes place entirely in peripheral lymphoid organs/tissues?
    A: The differentiated effector lymphocyte
  15. Q: Which 4 stages of lymphocyte maturation are only found in the bone marrow/thymus under normal conditions?
    A: Stem cell, pro-lymphocyte, pre-lymphocyte, immature lymphocyte, mature lymphocyte
  16. Q: Where might mature lymphocytes be found (2 places)?
    A: Bone marrow/thymus and peripheral lymphoid organ/tissue
  17. Q: Which stages of lymphocyte development experience early maturation and growth factor-mediated expansion?
    A: Stem cells and pro-lymphocytes
  18. Q: At which stage of lymphocyte development are antigen receptors expressed?
    A: Pre-lymphocyte
  19. Q: Which lymphocyte(s) can perform effector functions (give maturational stage (s))?
    A: Differentiated effector lymphocyte
  20. Q: What event follows stem cell proliferation and pre-B cell proliferation during B-cell maturation?
    A: RAG expression
  21. Q: At what stage does recombination of the H chain gene take place?
    A: Pre-B cell stage
  22. Q: At what stage does recombination of light chains take place?
    A: Immature B cell
  23. Q: At what stage does alternative splicing of the of VDJ-C RNA take place?
    A: Mature B cell
  24. Q: Can Ig be expressed in the absence of H chains?
    A: No
  25. Q: All stages of B cell maturation have the CD43 surface marker expressed except for which stage?
    A: Mature B cell stage
  26. Q: How is the response of the pre-B cell to antigen different from that of an immature B cell?
    A: Pre- B cells cannot respond to antigen
  27. Q: Where do B cells live longer: vasculature or marrow?
    A: Marrow
  28. Q: Clonal expansion of B-cells results in which four events?
    A: Antibody secretion, isotype switching, affinity maturation, and memory B cell formation
  29. Q: Cross linking of membrane Ig by antigen directly results in what event?
    A: Tyrosine phosphorylation
  30. Q: Cross linking of membrane Ig by antigen ultimately results in what signals?
    A: Transcription factors
  31. Q: To what entity might C3d be attached?
    A: A microbe
  32. Q: What is the fate of C3d attached to a microbe?
    A: It is recognized by the B-cell CR2 receptor, and the complex, together with the Ig alpha and Ig beta complex, activates the B-cell.
  33. Q: What four changes in phenotype function occur after the activation of B lymphocytes?
    A: Entry into the cell cycle, increased expression of B7-1/B7-2, increased expression of cytokine receptors (IL-2, IL-4), increased survival due to expression of antiapoptotic proteins (Bcl-X)
  34. Q: What is CD28?
    A: It is the receptor for B7-1/B7-2 on the helper T Cell.
  35. Q: Which cell, the B-cell or the T-cell, has the CD40 ligand?
    A: The T-cell
  36. Q: What signals helper T-cells to stimulate isotype switching by antibodies?
    A: CD40 ligation, cytokines
  37. Q: What other CD activates B cells?
    A: CD28
  38. Q: Without signals from helper T cells, which is the only antibody made?
    A: IgM
  39. Q: Is the "looping out" process reversible?
    A: No
  40. Q: What is the major Ig isotype secreted by the polyclonal activator LPS (lipopolysaccharide)?
    A: IgM
  41. Q: What is the difference between APC’s and FDC’s in terms of their location?
    A: APC’s migrate from tissue to lymphoid organs. FDC’s reside in the lymphoid organ.
  42. Q: How does the FDC respond to antigen?
    A: It binds to it but does not internalize it.
  43. Q: To what antigen do thymus-dependent antigens respond?
    A: Proteins
  44. Q: To what antigens do thymus independent antigens respond?
    A: Polymeric antigens, especially polysaccharides; also glycolipids, nucleic acid.
  45. Q: How do B cells know when to shut down?
    A: Antigen-antibody complexes bind to B cell Ig and Fc receptors blocking the B cell receptor signaling
  46. Q: During which B cell response to antigen is IgM the major product?
    A: Primary response
  47. Q: During which B cell response to antigen is there a high affinity of antibody for antigen?
    A: Secondary response
  48. Q: What are two ways to activate B-cells?
    A: T-cell dependent and T-cell independent antigen
  49. Q: CD40 is needed for which of the two pathways of B-cell activation?
    A: T-cell dependent B cell activation
  50. Q: Where does the T-cell see the antigen of presented by the B-cell?
    A: In the class II complex
  51. Q: Which are the known T-cell products that clearly stimulate B-cell proliferation?
    A: IL’s 2, 4, 5, and 13.
  52. Q: What do IL-2/IL-6 specifically do for B cells?
    A: Induce Ig secretion.
  53. Q: Chromosomal recombination is involved in which B-cell behavior?
    A: Isotype switching
  54. Q: What is the purpose of affinity maturation?
    A: To create Ig with higher affinity for antigen
  55. Q: What happens to those B cells that lose affinity for antigen?
    A: They are eliminated.
  56. Q: If further exposed to antigen, what response will T-cell independent antigens have?
    A: They will have no secondary response, and will only produce IgM isotypes of low affinity and poor quality.
  57. Q: Which serious recurrent bacterial infection is most commonly seen with an antibody deficiency?
    A: Sinopulmonary infections
  58. Q: The increase of monoclonal antibody such as IgG during an antibody deficiency syndrome may have what effect on other hormone levels?
    A: It depresses them.
  59. Q: Which type of immunity is not acquired from your mother?
    A: T-cell immunity
  60. Q: Stem cell abnormality, IL-2 receptor defect, ADA deficiency, and signal transduction defects are the features of which immune deficiency?
    A: Severe Combined Immune Deficiency
  61. Q: What is the typical duration of transient hypogammaglobulinemia?
    A: Two years
  62. Q: How is hypogammaglobulinemia typically treated?
    A: Immunize and check response. No treatment needed.
  63. Q: What major feature do Bruton’s Agammaglobulinemia and Hyper-IGM Syndrome share?
    A: Both are X-linked.
  64. Q: Which disease involves a B-cell tyrosine kinase gene abnormality?
    A: Bruton’s Agammaglobulinemia.
  65. Q: Bruton's Agammaglobulinemia is characterized by what (deficiency)?
    A: Absence or very low quantities of Ig on the surface of mature B-cells.
  66. Q: Bruton's Agammaglobulinemia: what part of the antibody is present in the pre B-cell cytoplasm?
    A: Mu heavy chains
  67. Q: Bruton's Agammaglobulinemia: why do infections begin between 4-6 months of age?
    A: Mother's immunoglobulin disappears.
  68. Q: Hyper-IGM Syndrome: what levels of IgM are common (2)?
    A: Normal to increased IgM
  69. Q: What is the cause of the deficiency of IgG,IgA, and IgE in Hyper-IGM Syndrome?
    A: Defect in class switching by block at IgM B-cell.
  70. Q: Hyper-IGM Syndrome: Lack of which B-cell ligand is responsible for the deficiency in class switiching?
    A: The CD40 ligand.
  71. Q: Is an immunoglobulin A deficiency common or rare?
    A: Very common
  72. Q: A clinical presentation of allergy, eczema, food allergies, with no immune exclusion of harmful antigens: which deficiency?
    A: IgA deficiency.
  73. Q: Should blood and blood products given to IgA deficient patients contain/not contain IgA?
    A: Not contain IgA- these can cause severe allergic reactions.
  74. Q: When is the onset of Common Variable Hypogammaglobulinemia?
    A: Several years after birth to 90 years.
  75. Q: Common Variable Hypogammaglobulinemia: what cells are involved?
    A: B and T cells
  76. Q: What type of infections are most common in Common Variable Hypogammaglobulinemia?
    A: Sinopulmonary infections.
  77. Q: What is the most common clinical symptom in Common Variable Hypogammaglobulinemia?
    A: Diarrhea
  78. Q: What growth factor deficiency is related to Common Variable Hypogammaglobulinemia?
    A: IL-2 deficiency
  79. Q: Herpes zoster, herpes simplex, cytomegalovirus, and enteroviral meningoencephalitis are viral infections associated with which immunodeficiency?
    A: Common Variable Hypogammaglobulinemia?
  80. Q: Common Variable Hypogammaglobulinemia: what is its etiology?
    A: Failure to terminally differentiate to plasma cells.
  81. Q: What are four indicated therapies for antibody deficiencies?
    A: Prevent life-threatening infections, decrease pulmonary damage, eradicate localized infection, replace gammaglobulin (in most instances).
  82. Q: What is one major hazard of gammaglobulin therapy?
    A: Anaphylaxis due to Ig’s
  83. Q: Recurrent bacterial infections, low IgG, and no antibody formation when immunized may indicated therapy (and route) for patients with hypogammaglobulinemia?
    A: IVIG