immuno chapter 7.txt

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immuno chapter 7.txt
2011-03-03 09:37:01
immuno chapter

Immuno chapter 7
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  1. ��Bone Marrow
    T cell progenitor cells leave before gene rearrangement can occur
  2. Thymus
    positive and negative selection
  3. Peripheral lymphoid orgasns
    encounter foreign antigens and are activated
  4. Migration to active sites
    activated t cells migrate to site of infection to activate macrophages or kill host cells or b cell area
  5. Path of t cells
    Born in bone marrow, travel to thymus to develop, once matured they circulate the secondary lymphoid tissues
  6. Why is the thymus a primary lymphoid tissue?
    it is only involved in development, not directly fighting infection
  7. What does the thymus contain?
    Thymocytes (immature T cells) and t cells, macrophages, dendritic cells, and thymic stroma (epithelial cell)
  8. Digeorge syndrome
    thymic epithelium does not develop so there is no thymus
  9. Thymus cortex
    Outer, close packed and consists of ECTOdermal cells; contain thymocytes and macrophages
  10. Thymus medulla
    Inner, less dense consists of endodermal cells; contains theymocytes, dendritic cells, and macrophages
  11. Thymic anlage (early thymus)
    the combination of the ectodermal cells early in development that is later colonized by progenitor cells from the bone marrow
  12. Involution
    replacement of thymus tissue with fat tissue after puberty
  13. What occurs in the early stage of development?
    • progenitor stem cells enter the thymus but do not have t cell markers
    • stem cells persist in the thymus and start to aquire the correct receptors, adhesion molecules and signaling molecules (IL-7 is secreted by thymic stromal cells and helps develop t cells)
    • begin to rearrange TCR genes
  14. DN thymocytes
    have t cell characteristics but no CD4, CD8, CD3, or TCR
  15. IL-7
    secreted by thymic stromal cells and binds to IL-7 receptor on CD34+ cells
  16. Notch 1 receptor
    on thymocytes; binds to ligands on thymic epithelial cells
  17. What signals do IL-7 and notch 1 initiate?
    they result in the removal of repressive transcription factors
  18. What occurs in the middle stage?
    TCR gene rearrangement starts for DN thymocyte;Becomes a DP thymocyte when CD4 and CD8 are expressed due to beta rearrangement.
  19. pre-TCR
    pTalpha holds the beta chain in place
  20. What composes the pre-TCR
    pTalpha and beta
  21. What does the pre-TCR signal
    the termination of arrangement
  22. What is the first checkpoint?
    to determine if the beta chain has the potential to bind to alpha chains
  23. What happens if the pre-TCR passes the checkpoint?
    it becomes a pre-T cell
  24. beta chain has how many chances to rearrange
  25. What happens with successful beta rearrangment?
    pre-TCR formation and RAG shut down
  26. What segments does the alpha chain have?
    V and J; has many j segments so successful rearrangment is likely
  27. what is excised during alpha rearrangment?
    delta loccus
  28. What happens when the alpha chain is successfully rearranged?
    it pairs with the beta chain and shuts down RAG
  29. Positive selection
    Developing T cells that recognize self will be positively selected
  30. Negative selection
    developing t cells that bind too tightly to self will be negatively selected
  31. What is the end result of positive and negative selection?
    t cells will bind to self moderately well
  32. Single positive thymocyte
    positive selection determines if a T cell will become CD4 or CD8 depending on which MHC it binds
  33. Regulatory T cells
    CD4 t cell that binds self antigens and suppresses other CD4 T cells that can bind to the same APC
  34. Are there more CD4 or CD8 cells?
    twice as many CD4
  35. Bone marrow transplant
    GHD occurs when mature t cells from the donor attack the host
  36. Organ rejection
    Host immune system attacks transplanted organ if rejected
  37. Immunotherapy
    Tumor therapy- select, enrich and amplify TILs