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

Phosphorylation of integrin ot chains too, has been described . In the 02 family, all three a subunits are constitutively phosphorylated in PMN and monocytes (28) , but this phosphorylation does not appear to play, at least for «L, any functional role. In the VLA family, a subunit phosphorylation correlates with the high avidity state of integrin receptor. Phosphorylation of the cytoplasmic domain of cx6 subunit and its association to increased adhesion to LM has been observed in our study and in activated murine macrophages (11) . c16 phosphorylation suggests an important functional role of a subunit cytoplasmic domain in affinity regulation of integrin receptors. Supporting this idea, recent evidence show that affinity of cilIbO3 is modulated by the cytoplasmic domain of celIb subunit (29) . Indeed, its truncation resulted in increased affinity for fibrinogen similar to that observed after exogenous platelet activation . Overall, it can be hypothesized that a sequence in the cytoplasmic domain of ot subunit may maintain integrin receptor in a low affinity conformation, likely interacting with an intracellular moiety with "repressor" activity. Modification of this interaction, which can be induced by cytoplasmic domain truncation or phosphorylation, as shown in our study and by Shaw et al . (11) , may then result in induction of a high affinity state .