Term
| function of a lymphocytes uropod? |
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Definition
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Term
| T cell co receptors and what they bind |
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Definition
LFA 1, binds ICAM1 in immunological synapse
CD28, to interact with B7 |
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Term
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Definition
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Term
| steps in T-cell binding to peptide-MHC |
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Definition
1) T cell initialy binds APC through low affinity LFA-1:ICAM-1
2) Binding of TCR to peptide-MHC signals a conformational change in LFA-1
3) get increased affinity of LFA-1 for ICAM-1 and prolongs cell-cell contact |
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Term
| two reasons why B and T cells are able to leave circulation |
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Definition
- low shear force and charge
- adhesion molecules in the venule |
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Term
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Definition
1) initiated by binding by lymphocyte L-selectin to sulfated carbohydrates of vascular addressins GlyCAM-1 and CD34
2) activation of LFA-1 by chemokines, which regulate the expression of integrins like LFA-1 on leukocytes.
3) arrest/adhesion of lymphocyte by binding of LFA-1 to ICAM-1
4) Migration and unzipping of adhesion molecules
5) digestion of the basal lamina as it becomes part of the parenchyma of lymphnode |
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Term
| Why do B cells move to follicles? |
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Definition
- they express receptors (CXCR5) for a B lymphocyte chemoattractant (BLC) made by FDC.
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Term
| How to T cells enter lymph node? How do they leave? |
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Definition
enter through HEV
Leave via efferent lymphatics |
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Term
| Why do T cells remain in the deep cortex? |
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Definition
| - they express receptors (CCR7) for the chemokine MIP-3β (CCL19) and CCL21 mad by reticular stromal cells and mature DCs in deep cortex. |
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Term
What is FTY720 used to treat?
What is its mechanism of action? |
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Definition
- FTY720 is used to treat multiple sclerosis
- traps lymphocytes in lymph node, preventing them from acting in the autoimmune reaction |
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Term
How long to B and T cells stay in the lymp node?
How do they leave? What molecule is important?
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Definition
12 hours
leave via HEV, using lipid molecule spingosine-1-phosphate |
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Term
how does T-cell trapping work?
how long does it take for entrapment? How long does it take for migration out of the lymph node |
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Definition
- T cells that recognize their specific antigen in the lymph node bind stably to their APC and are activated, resulting in production of armed effector cells that are "trapped." this may take about 5 days.
- After day 5, they leave the lymph node in large number activated. |
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Term
| Steps in B and T cell migration to lymph nodes |
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Definition
1) stromal cells and HEV epithelial cells secrete CCL21
2) DC's have a receptor for CCL21 and migrate into the developing lymph node
3) DC's secrete CCL18 and CCL19 which attract T cells and B cells
4) B cells induce follicular DC's which in turn secrete CXCL13
5) CXCL13 binds outside B cells at their CXCR5 receptors and attracts them in. |
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Term
Where do cells go first in the spleen?
Where to T cells go?
Where do B cells go? |
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Definition
-marginal zone blood sinus
- T cells: PALS
- B cells: follicles and marginal zone |
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Term
how long do B and T cells stay in the spleen?
How do they leave? |
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Definition
- both stay 5 hours
- leave via red pulp sinusoids to open circulation |
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Term
What changes in expression do naive T cells under go as they become armed effector T cells?
What is the result of this? |
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Definition
- decrease expression of L-selectin
- increase expression of LFA-1 and VLA-4
- armed effector T cells are not readily found in secondary lymphoid organs; they will interact with peripheral vascular endothelium instead of lymph node HEV |
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Term
| what is the CD change that the naive T cell under goes? What does this result in? |
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Definition
CD45RA -> CD45RO
- CD45RO makes effector T cells more sensitive to stimulation by specific antigen |
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Term
What do immature DC cells express?
What is another important characteristic?
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Definition
- express DEC205 receptors and E-cadherin molecules
- they have low MHC and low costimulatory molecules
- they are phagocytitic |
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Term
What do DC cells do after activation of their TLR by antigen?
- where do they travel
- what do they up regulate |
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Definition
- Travel to lymphoid tissue
- upregulate CCR7, which binds to CCL19 and CCL21 which urther promotes maturation |
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Term
What molecules are expressed by mature dendritic cells (5)
What do they produce to attract T-cells? |
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Definition
- MHC II
- B7 (CD80)
- CD40
- ICAM
-LFA
- CCL19 and CCL21 |
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Term
| three places for mature DCs and what they do there? |
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Definition
- lymph node for T-cell activation
- thymus for negative selection
- GI tract as "sentinels" |
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Term
Where are follicular dendritic cells found?
What are they probably derived from?
What is their important receptor?
What else do they express? |
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Definition
- germinal center light zone
- probably from stromal cells
- FCγR
- ICAM-1, VCAM-1 |
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Term
What important chemokine to FDC's produce?
What does it attract? |
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Definition
CXCL13
-B cells by binding CXCR5 |
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Term
What forms the first immunological synapse?
What forms the second immunological synapse?
What forms the third immunological synapse? |
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Definition
synapse I: between DC and Th0->Th1
Synapse II: between Th2 and inactive B cell
Synapse III: Th2/F and active B cell |
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Term
| antigen specific naive B cells are trapped at the border between the T zone and the follicle and are stimulated to proliferate; they then have two fates: |
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Definition
1) go to medullary cord and divide, differentiate and secrete antibody into the circulation for several days
2) some migrate into nearby follicle forming a germinal center where rapid proliferation and somatic hypermutation can occur |
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Term
| Difference between synapse II and III? |
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Definition
- synapse II forms at the edge of the follicle between antigen primed B cells and antigen specific Th cells. These then go into the dark zone where they proliferate and undergo somatic hypermutation
- These centrocytes that survive selection with FDC upregulate Bcl-xl and migrates up to light zone where synapse III can occur between another Th cell |
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Term
| Two types of synapse III and their effects |
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Definition
- if B cell in light zone interacts with Th2, IL4,5,6, will cause it to further proliferate
- if B cell in light zone interacts with Th1, INFγ will be produced and the centrocyte will switch isotypes and produce IgG2a and IgG3. |
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Term
| difference beween spllena dn lymph node creating immune response? |
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Definition
| - antigen enters spleen in the white pulp through the marginal sinus. |
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