Provisional mechanism for the activation of the NADPH oxidase by the LRI. The LRI and the IAP are thought to form a complex in the leukocyte plasma membrane. When leukocytes are in suspension, the signal transduction pathway between this complex and the NADPH oxidase is blocked. The blockade is lifted by the following combination of events: (1) the binding of LRI to entactin, a basement membrane protein; (2) adhesion of the phagocyte to a surface (in suspended cells, NADPH oxidase is not activated by the binding of LRI to entactin); and (3) possibly a conformational change in IAP. These events somehow activate protein kinase C, which then activates the oxidase. Tyrosine phosphorylation does not participate in oxidase activation by LRI/IAP.96