EVIDENCE FOR INTEGRINS OTHER THAN BETA(2) ON POLYMORPHONUCLEAR NEUTROPHILS - EXPRESSION OF ALPHA(6)BETA(1) HETERODIMER

The expression of non-beta2 integrins on polymorphonuclear neutrophils (PMNs) was analyzed by immunoprecipitation and flow cytometry using p latelet-free PMN preparations and anti-Fc-gammaR blocking mAbs. No bet a3 integrin was detected with six anti-beta3 mAbs. Conversely, integri n beta1 chain was present on PMNs, although at low level, and could be distinguished from platelet beta1 by SDS-PAGE. The MW differences dis appeared after N-glycanase treatment. PMNs express only 2500 molecules of beta1 per cell and this expression is not modulated by agonists su ch as phorbol myristate acetate, formylmethionyl-leucyl-phenylalanine, granulocyte-macrophage colony-stimulating factor, or tumor necrosis f actor alpha, which enhance CD11b expression, or by interferon-gamma or transforming growth factor beta. PMNs were found to express alpha6 as sociated with beta1, and no reactivity was observed with various anti- alpha1, anti-alpha2, anti-alpha3, anti-alpha4, anti-alpha5 or anti-alp ha(v) mAbs. In conclusion, although other leukocytes express various b eta1 integrins, which mediate cell interactions with ECM proteins, PMN s appear to express only the laminin receptor alpha6beta1. PMN interac tions with nonlaminin ECM ligands thus seem to be mediated either excl usively by beta2 integrins or by nonintegrin molecules.