Type I collagen is present in connective tissue and bone where it makes up about 90% of the organic matrix. Defects in one or both alleles of the type I collagen gene causes "brittle bone disease" (osteogenesis imperfecta). Patients suffering from such defects have low levels of fully functional type I collagen resulting in fragile bones. This antibody is highly specific for native type I collagen and shows no evidence of cross-reactivity with type II, III, V and VI collagens in inhibition ELISA and immunoblotting, and no evidence of cross-reactivity with other connective tissue proteins (laminin, fibronectin, elastin). The antibody reacts with human, calf, sheep, pig, dog and goat type I collagens in ELISA and immunoblotting, but does not react with mouse, guinea pig, cat, rabbit, squirrel, horse, kangaroo or chicken type I collagen. The antibody has a Ka of approximately 2.5 x 106 M-1 for human type I collagen.