The flashcards below were created by user
on FreezingBlue Flashcards.
Central lymphoid organs?
Peripheral lymphoid organs?
1- thymus and bone marrow
2- Lymph node, Spleen, MALT
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)
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)
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)
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
Naiive B-cells express:
- Naive B cells have CXCR5 receptor,
- which binds:
- CXCL13 in the follicles of the LN
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
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
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
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
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