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LECTURE 7 March 1st, 2011
MIDTERM: 36 multiple choice questions; 2158 in the medical sciences building for the
Location is the lecture room
Todays 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 network of conduits carrying lymph
oAnything dangerous is put into lymph nodes, where they are
oEfferent going in
oAfferent where lymphocytes leave the nodes
Lymph interstitial fluid in tissues 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 filter agent for blood
oLymph nodes filter agent for lymph
Dont need all lymph nodes to control body
oMany can be absent
oIf one is absent the next one can take over the responsibilities
Migration of lymphocytes
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 adhesion molecules

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Lymphocytes know where to jump off highway to get into lymph
At places where lymph nodes branch off from blood vessel,
elevated endothelial venules are there
oHEV so lymphocytes can enter lymph node tissue
by squeeze through endothelial cell tissue into node
oEndothelial cells raised as HEV
Lymphocyte migration no flat surface
oT-cell 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-
Still very effective for T-cells to interrogate their
Chemokine receptors look funny adhesion receptor bind to adhesion
oDirectional cue to lymphocyte 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 these lymph nodes
will increase expression of adhesion molecules and
oWant to concentrate antigen-specific Tcell to the lymph node thats
draining the site of infection
Upregulate so lymphocytes will preferentially go to this
particular lymph nodes, so can get right lymphocytes at the
right place at the right time
Fever optimize getting cells to appropriate lymph node to
get the adaptive immune response
A little fever is thus good
Naïve T-cell from blood, squeezes through HEV, and goes into lymph node tissue,
spend time in node
If everythings fine, will leave through efferent and repeat the same
If infection in tissue bed that drains the particular lymph node,
oTissue bed drains lymph into lymph node
If lymphocyte isnjt antigen specific, doesnt see anything dangerous
spend time in node and then leave through efferent lymphatic as naïve T-
oEfferent lymph collected in thoracic duct
oTwo ducts collect all lymph from body
**CORRECTION efferent and afferent on the definition page
Afferent lymphatic system drains tissue bed
Naïve lymphocyte doesnt go into tissue never goes into tissue
What are lymph nodes?
Extremely organized structure
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