Characterization of eosinophil adhesion to TNF-alpha-activated endotheliumunder flow conditions: alpha(4) integrins mediate initial attachment, and E-selectin mediates rolling

The multistep model of leukocyte adhesion reveals that selectins mediate ro lling interactions and that integrins mediate firm adhesion processes. In t his study, the interaction between eosinophils and TNF-alpha-activated HUVE C (second or third passage) was studied under flow conditions (0.8 and 3.2 dynes/cm(2)). Especially the role of ct, integrins on eosinophils and E-sel ectin on HUVEC was studied. Inhibition of the integrin a, chain on eosinoph ils reduced the number of firmly adhered resting eosinophils to TNF-alpha-s timulated endothelium by 43% whereas the percentage rolling cells increased 2.2-fold compared with untreated control eosinophils. Blocking of E-select in on the endothelium reduced the number of adherent eosinophils by only 23 % and 16%, In this situation, however, hardly any rolling adhesion was obse rved, and the few rolling cells showed a low rolling velocity, Blocking bot h alpha(4) integrin on eosinophils and; E-selectin on HUVEC reduced the num ber of adhered eosinophils by 95%, P-selectin did not significantly partici pate in eosinophil adhesion to TNF-alpha-activated HUVEC, Inhibition of bot h alpha(4) integrins and beta(2) integrins on eosinophils resulted in a red uction of adhered cells by 65% and a 3-fold increase in percentage rolling cells. Taken together, these results clearly show that resting eosinophils preferentially use constitutively active, alpha(4) integrins (alpha(4)beta( 1), alpha(4)beta(7)) for the first attachment to TNF-alpha-activated HUVEC, In addition, alpha(4) integrins and E-selectin work synergistically in eos inophil adherence to TNF-alpha-activated HUVEC, Although E-selectin is impo rtant for eosinophil rolling under these conditions, beta-selectin plays on ly a minor role.