(A) Constructs containing full-length (Fl) Mfge8, Mfge8 lacking the terminal discoidin domain (Dd1), or both discoidin domains (Ndd) fused to a huFc domain were immobilized on a Biacore CM5 chip, and binding to increasing doses of collagen was evaluated. P/T represents a domain present in the long isoform of Mfge8 that is rich in proline and threonine. (B) Collagen bound full-length Mfge8 in a dose-dependent fashion with a Kd of 733 nM. (C) Flow plot demonstrating dose-dependent binding of collagen to immobilized full-length construct. Black line, 16 nM; filled squares, 31 nM; open diamonds, 63 nM; filled circles, 125 nM; open triangles, 250 nM; filled diamonds, 500 nM. (D) Flow plot demonstrating dose-dependent binding of collagen to immobilized Dd1 construct. (E) Flow plot demonstrating no binding of collagen to the Ndd construct. (F) The ability of constructs (13 μg/ml) to rescue the defect in alveolar macrophage collagen uptake was evaluated in vitro. Dd1 construct rescued Mfge8–/– alveolar macrophage collagen uptake, while the Ndd construct had no significant effect (*P = 0.01, 1-way ANOVA with Bonferroni t test; n = 3–4). Data are presented as mean ± SEM.