S. D. Wright investigated how receptors of phagocytes connect recognition of coated targets with distinct cellular responses. With S. C. Silverstein, Wright compared hydrogen peroxide release from granulocytes, monocytes and macrophages spreading on surfaces coated with different ligands. The 1983 study found strong release on IgG-coated surfaces but little on surfaces carrying C3b or iC3b, historically written C3bi.[ref]
The useful mechanistic distinction was between engulfment and an oxidative response. Under conditions combining fibronectin with complement ligands, the cultured monocytes showed a strong phagocytosis response without measurable hydrogen peroxide release.[ref]
Receptors for C3b and C3bi promote phagocytosis but not the release of toxic oxygen from human phagocytes by S. D. Wright and S. C. Silverstein. Abstract; fibronectin/C3-coated surfaces and dissociation of the two outcomes
Thus receptor engagement does not specify one indivisible activation state. Measuring only uptake would miss a difference revealed by measuring a second output. New to topics? Read the docs here!