Evidence for integrins other than beta 2 on polymorphonuclear neutrophils: expression of alpha 6 beta 1 heterodimer

The expression of non-beta 2 integrins on polymorphonuclear neutrophils (PMNs) was analyzed by immunoprecipitation and flow cytometry using platelet-free PMN preparations and anti-Fc gamma R blocking mAbs. No beta 3 integrin was detected with six anti-beta 3 mAbs. Conversely, integrin beta 1 chain was present on PMNs, although at low level, and could be distinguished from platelet beta 1 by SDS-PAGE. The MW differences disappeared after N-glycanase treatment. PMNs express only 2500 molecules of beta 1 per cell and this expression is not modulated by agonists such as phorbol myristate acetate, formylmethionyl-leucyl-phenylalanine, granulocyte-macrophage colony-stimulating factor, or tumor necrosis factor alpha, which enhance CD11b expression, or by interferon-gamma or transforming growth factor beta. PMNs were found to express alpha 6 associated with beta 1, and no reactivity was observed with various anti-alpha 1, anti-alpha 2, anti-alpha 3, anti-alpha 4, anti-alpha 5 or anti-alpha V mAbs. In conclusion, although other leukocytes express various beta 1 integrins, which mediate cell interactions with ECM proteins, PMNs appear to express only the laminin receptor alpha 6 beta 1. PMN interactions with non-laminin ECM ligands thus seem to be mediated either exclusively by beta 2 integrins or by nonintegrin molecules.