Triggering through CD16 or phorbol esters enhances adhesion of NK cells to laminin via very late antigen 6

Very late antigens VLA-1, VLA-2, VLA-3, and VLA-6, belonging to the beta1 subfamily of integrins, have been identified as receptors for different binding domains of laminin (LM). We have detected VLA-6, but not VLA-1 and VLA-2 on a subset (50-70%) of fresh peripheral blood CD3-, CD16+, CD56+ human natural killer (NK) cells by immunofluorimetric and biochemical analysis. Binding assays performed on LM-coated plates showed that 10-15% of NK cells spontaneously adhere to LM, and this adhesion is mediated by VLA-6. Activation of NK cells through CD16 triggering or by phorbol ester results in a rapid increase of adhesion to LM, which is still mediated by VLA-6. The enhanced adhesiveness is not associated with changes in beta1 LM receptor expression, while it correlates with changes in the phosphorylation status of alpha6 subunit. The expression of VLA-6 on NK cells and the modulation of its avidity by activating stimuli may be relevant for NK cell migration and tissue location during inflammation or immune response.