During the immunological response, circulating leukocytes are recruited from the blood system towards inflammatory zones via a complex cascade of events: after exiting the capillary bed, leukocytes stop by adherence in the post-capillary veinules, and then migrate on the vessels walls where eventually cross the endothelium. In an attempt to decipher some mechanical aspects involved in these processes, we have used in vitro approaches to control the micro-environment properties of single cells. In a fist part, we will discuss the roles of adhesion, friction and deformability in the arrest of leukocytes in blood capillaries, which is the triggering event of the acute respiratory distress syndrome (ARDS). In a second part, we will show how hydrodynamic shear stresses encountered in blood vessels can guide the migration of leukocytes on the inner surface of blood vessels.

Olivier THEODOLY, Laboratoire Adhésion & Inflammation (LAI), INSERM/CNRS/AMU, Marseille.
with : P Preira, P Nègre, P Robert, A Lellouch, MP Valignat, P Bongrand (LAI); J Bico (ESPCI); JM Forel, L Papazian (AP-HM); A Asnacios, F Gallet, S Henon (MSC).