Immuno 4 Leuk traff

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Anonymous
ID:
64956
Filename:
Immuno 4 Leuk traff
Updated:
2011-02-08 09:42:03
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Leukocyte Immuno
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Description:
Leukocyte trafficking
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  1. Central lymphoid organs?

    Peripheral lymphoid organs?
    1- thymus and bone marrow

    2- Lymph node, Spleen, MALT
  2. Lymph Node:
    Paracortical Area:
    Medullary Cords:
    Primary Lymphoid Follicle:
    Secondary Lymphoid Follicle:
    • Paracortical Area: T cells + B cells
    • Medullary Cords: macrophages + plasma cells
    • Primary Lymphoid Follicle: resting B cells
    • Secondary Lymphoid Follicle: with GERMINAL CENTERS (site of intense Bcell proliferation)
  3. How does a DC in the tissues know to go to the LN?
    • it has TLR receptors (which recognize PAMPs on microbes)
    • it has TNFalpha and IL-1 receptors (which recognize inflammatory cytokines produced by macrophages at the site of inflammation)
  4. What changes occur when a DC is activated?
    • Activated DC: becomes antigen presenting (instead of immature antigen capturing DC):
    • Increases expression of 2 signals required for Tcell activation:
    • 1. MHC 1 and 2
    • 2. Costimulatory Molecules (B7-1: CD80, CD86)
  5. What pulls the activated DC into the LN?
    • Activated DC's increase expression of CCR7 receptor which binds to:
    • CCL19 and CCL21 chemockines in the Tcell zone (paracortical area) of the lymph node
  6. Naiive B-cells express:
    • Naive B cells have CXCR5 receptor,
    • which binds:
    • CXCL13 in the follicles of the LN
  7. How does the spleen serve a similar function to the lymph nodes response to lymph-borne antigens?
    • Blood-bourne antigens go to the spleen--> travel through the red pulp sinusoids --> arrive at the WHITE PULP (lymphocyte-rich region) near artery -->
    • Tcells go to Periarteriolar lymphoid sheaths
    • & Bcells go to the follicle
  8. Naiive T cells express:
    • Naiive T cells: L-Selectin (CD 62L)
    • which binds with LOW AFFINITY to
    • carbohydrate ligands on the endothelial cells lining the HEV (high endothelial venule)
    • and induces rolling of the Tcell
  9. Once the Tcell gets to the LN and CCR7 binds CCL19 + CCL21, what happens?
    • binding of CCR7 + CCL19/CCL21 causes expression of
    • HIGH AFFINITY integrins: LFA-1 and VLA-4
    • which induce high affinity binding of Tcell to HEV (and cause migration into the LN stroma)
    • *B cells have similar mechanism
  10. What changes occur in an Activated T cell?
    • Activated Tcell:
    • DOWNREGULATES: L-selectin + CCR7
    • UPREGULATES: Adhesion molecules and chemokine receptors:
    • ^E-selectin (CLA-1), CCR4, CCR10
    • which bind to inflammatory cytokines at the endothelium of infection sites: CCL 17 + CCL27
  11. Effector Bcells are homed to:
    • Effector Bcells are homed to the bone marrow (where they set up shop as long lived plasma cells)
    • *exception: Bcells that produce IgA isotype Ab: often traffic to the mucosal sites

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