Celladhesionisafundamentalfeatureofmulticellularorganismsincludingtheirdefensemechanisms.Inthelatercaseinmammals,leukocytesplaycentralrole.Theybindbacteria,parasites,viruses,tumorcellsetc.FurThermore,theirinteractionswiththeendotheliumareofspecialimportance.Generally,lymphocyteadhesionandpassagefromthebloodstreamtothelymphaticsystemoccursinthehighendothelialvenulesofthelymphnodes.Thiswaythelymphocytescancommunicatewitheachotherinthelymphaticsystemandsearchforforeigncompoundsaftertheirrecirculationtothebloodstream,thisfulfillingtheirroleintheimmunesystem.Thereactionpassesthroughthefollowingsteps:1.Rolling(theflowofcellsissloweddownbyfirstmakingcontactstotheendotheliumviaP-,E-,andL-selectinsandtheirreceptors);2.Adhesion(Afteractivationofleukocyteintegrins,firmcontactsareestablishedbetweenthemandendotheliummoleculesoftheIgsuperfamily-LFA-1,Mac-1,VLA-4etc.);3.Flatteningofthecellsanddiapedesis(Adheringleukocytescrawltoanintercellularjunctionoftheendotheliumandthentransmigratetooreventhroughtheintercellularmatrix.ThisismediatedbyahomophilicinteractionsofPECAMandCD31.

Contributor:KosiGramatikoff,PhD

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