MW L4 Leukocyte Chemotaxis Flashcards
4 steps if leukocyte diapedesis
- circulating
- tethering/rolling
- firm adhesion
- transmigration
What is a leukocyte?
WBC
What guides tethering and rolling
selectins - specific homing receptors and their ligands
3 types of selectins
what expresses them
L (leucocytes)
P (platelets & endothelium)
E (endothelium)
What do L-selectins bind to?
Carbohydrates on the endothelium
Which selectins bind leukocytes?
P and E
L-selectin activation leads to….(2)
transient increase in avidity
rapid shedding by proteolytic cleavage (‘shedase’)
Where is P selectin stored?
When does it translocate to cell surface?
In granules
On cell activation (thrombin, histamine)
E selectin expression is induced by ….. (2)
cytokines
or
LPS
Expression of E selectin requires
de novo synthesis
Glucocorticoid effect on selectins?
E selectin is inhibited
LAD II stands for
leukocyte adhesion deficiency II
Pts with LAD II have normal ………………… in vitro
phagocytosis and respiratory burst
Pts with LAD II have defective …………. metabolism
this causes,,,,
fructose
leukocytes do not express selectins
LAD II causes decreased rolling response on ………. or ………
E or P selectins
severely impaired ……………………. in skin inflammation with LAD II
<90% decreased
Rolling along the endothelial surface activates …………..
where…………
Integrins
on the LEUKOCYTE surface
Integrins are …….. proteins
expressed where?
heterodimeric
expressed on the surface of leukocytes and most other cells
Integrins have a common ……. chain
Beta2 chain
There are ………… forms of alpha chain
this means ……… heterodimers are formed
3
alpha L /beta 2
alpha M/ beta 2
alpha X/ beta 2
Leukocyte adhesion changes avidity and affinity how?
Conformational change - affinity
Clustering of integrins - avidity
LAD I or II has pus?
neither - both have recurrent infections
LAD I what do leukocytes do in vitro?
they do not adhere to extracellular material
ICAM are…
intercellular adhesion molecules
