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1 Mar 2011
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LECTURE 7 โ€“ March 1st, 2011
MIDTERM: 36 multiple choice questions; 2158 in the medical sciences building for the
tutorial
๎€Location is the lecture room
Todayโ€™s material will not be on the midterm
Anatomical context where immune responses take place in body
๎€Movies are not testable material, just to fill in knowledge
How do lymphocytes move around the human body?
๎€Lymphocyte migration
oLymphocytes always moving throughout body
oNeed to patrol body for infection, tumour cell growth or antigen, anything
dangerous or foreign to host
๎€Lymphatic system โ€“ network of conduits carrying lymph
oโ€œplumbingโ€
oAnything dangerous is put into lymph nodes, where they are
โ€œinterrogatedโ€
oEfferent โ€“ going in
oAfferent โ€“ where lymphocytes leave the nodes
๎€Lymph โ€“ interstitial fluid โ€“ in tissues โ€“ found between cells of body
oEnters lymphatic vessels to be sampled in the lymph nodes
๎€Systemic infection, for example, spleen is first point of contact with immune cells
with pathogen
oSpleen โ€“ filter agent for blood
oLymph nodes โ€“ filter agent for lymph
๎€Donโ€™t need all lymph nodes to control body
oMany can be absent
oIf one is absent โ€“ the next one can take over the responsibilities
Migration of lymphocytes
๎€Chemokines
๎€T cell will move towards chemokines
๎€T-cell chemokines different from b cell chemokines
oImportant to orchestrate cellular interactions for an immune response
๎€Chemokines work in a gradient
oImagine a drop of colouring into water
oConcentration brightest at the source of chemokines
๎€Lymphocytes would keep going around in blood forever
oBut most infection they deal with are in tissue beds
oSo must enter lymph nodes to check for pathogen
oThey do so by sticking to endothelial cells of blood vessels, sense a
chemokine gradient, and then squeeze through endothelial cells to get
into tissues
๎€Proteins mediating sticking to the cells โ€“ adhesion molecules
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๎€Lymphocytes know where to jump off highway to get into lymph
nodes
โ€ขAt places where lymph nodes branch off from blood vessel,
elevated endothelial venules are there
oHEV โ€“ so lymphocytes can enter lymph node tissue
by squeeze through endothelial cell tissue into node
oEndothelial cells raised as HEV
๎€Lymphocyte migration โ€“ no flat surface
oT-cell โ€“ T-cell receptor, CD3, 4, or 8 sticking out; adhesion molecules
sticing out too; receptors for chemokine gradients sticking out too
๎€Sensing molecules are stuck on microvilli, projections off T-
โ€ขStill very effective for T-cells to interrogate their
environment
๎€Chemokine receptors look funny โ€“ adhesion receptor bind to adhesion
oDirectional cue to lymphocyte โ€“ thus chemokine not cytokine
๎€If sick and have fever, know adhesion receptors on surface of endothelial
cells are up regulated (many of them, instead of one or two)
oChemokine are more intense
oLymph node draining upper respiratory tract โ€“ these lymph nodes
will increase expression of adhesion molecules and
oWant to concentrate antigen-specific Tcell to the lymph node thatโ€™s
draining the site of infection
๎€Upregulate โ€“ so lymphocytes will preferentially go to this
particular lymph nodes, so can get right lymphocytes at the
right place at the right time
๎€Fever โ€“ optimize getting cells to appropriate lymph node to
get the adaptive immune response
โ€ข A little fever is thus good
Naรฏve T-cell from blood, squeezes through HEV, and goes into lymph node tissue,
spend time in node
๎€If everythingโ€™s fine, will leave through efferent โ€“ and repeat the same
๎€If infection in tissue bed that drains the particular lymph node,
oTissue bed drains lymph into lymph node
๎€If lymphocyte isnjโ€™t antigen specific, doesnโ€™t see anything dangerous โ€“
spend time in node and then leave through efferent lymphatic as naรฏve T-
oEfferent lymph collected in thoracic duct
oTwo ducts collect all lymph from body
**CORRECTION โ€“ efferent and afferent on the definition page
๎€Afferent lymphatic system drains tissue bed
๎€Naรฏve lymphocyte doesnโ€™t go into tissue โ€“ never goes into tissue
What are lymph nodes?
๎€Extremely organized structure
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Document Summary

M idterm: 36 multiple choice questions; 2158 in the medical sciences building for the tutorial. Today"s material will not be on the midterm. Anatomical context where immune responses take place in body. movies are not testable material, just to fill in knowledge. Lymphocyte migration: lymphocytes always moving throughout body, need to patrol body for infection, tumour cell growth or antigen, anything dangerous or foreign to host. Lymphatic system network of conduits carrying lymph: plumbing , anything dangerous is put into lymph nodes, where they are. Interrogated : efferent going in, afferent where lymphocytes leave the nodes. Lymph interstitial fluid in tissues found between cells of body: enters lymphatic vessels to be sampled in the lymph nodes. systemic infection, for example, spleen is first point of contact with immune cells with pathogen: spleen filter agent for blood, lymph nodes filter agent for lymph.

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