Binding of antibodies D4.6 and C6.7 to solid phase TSP. Ten micrograms/milliliter Ca-TSP or NEM-TSP (prepared as in Fig 7) in 2 mmol/L Ca²⁺ (▧) or 3 mmol/L EDTA () was coated on the microtiter plate overnight at 4°C. MoAbs D4.6 or C6.7 in either Ca²⁺- or EDTA-containing buffers were added and the immunoassay was performed as described in Materials and Methods using a 1-hour incubation at room temperature. The maximum binding for TSP in the presence of EDTA was taken as 100%. The results (means ± SE of three separate experiments) are expressed as the percent of maximum.