S. C. Silverstein

S. C. Silverstein studied the experimental cell biology of phagocytosis. Joint work with S. D. Wright showed that complement system receptor-mediated uptake and release of hydrogen peroxide could be separated by comparing ligand-coated culture surfaces.^[ref]

A 1984 study asked a further physical question: how accessible is the interface between a macrophage and its target? The authors compared access of soluble proteins beneath macrophages spread on glass with access beneath macrophages on surfaces coated with ligands promoting phagocytosis. The first interface admitted proteins with molecular mass as large as $200000$, whereas the ligand-coated interface excluded even tested proteins of molecular mass $50000$.^[ref]

This supported formation of a seal around the contact region, helping explain why an external scavenging enzyme might fail to reach locally released material. It is a compartment-access experiment: exclusion of the tested proteins does not establish impermeability to every small molecule. The example connects a cellular process with a measurable physical boundary.