Fig. 8.

The specific binding of SP-A to type II cells is blocked by P63 Ab. Type II cells were incubated with P63 Ab or nonimmune IgG (25 μg protein/ml) for 15 min followed by addition of increasing concentrations of ¹²⁵I-SP-A for 1 h at 4°C. A: total binding of SP-A. Data are means ± SE of 3 experiments performed in duplicate. *Statistically significant difference from binding of SP-A alone or with rabbit nonimmune IgG. B: binding of ¹²⁵I-SP-A in A expressed as total, nonspecific, and specific binding. The nonspecific SP-A binding data reflects the binding of SP-A in the presence of P63 Ab. The specific SP-A binding curve can be superimposed on the amount of SP-A blocked by the presence of P63 Ab [determined by subtracting the binding of SP-A with anti-P63 Ab present (open triangles) from that without additions (closed circles)].