Fibronectin, but not decorin, mediates its effects through β₁-integrin receptors.

(A) Adhesion of macrophages to fibronectin is mediated by a β₁-integrin. The 10 000 cells, previously stimulated with 1 mM RGD peptides or 5 μg/mL anti-β₁ antibodies for 1 hour, were cultured for 60 minutes on plates precoated with 10 μg/mL BSA (control) or 10 μg/mL decorin or fibronectin. Macrophage adhesion was analyzed by crystal violet staining. Each determination was made in triplicate, and the values represented correspond to the mean ± SD of 2 independent experiments. (B) The effect of fibronectin, but not that of decorin, on macrophage proliferation was inhibited by anti-β₁ antibodies. Macrophages cultured as in panel A were stimulated with 1000 U/mL M-CSF and their proliferation was analyzed by [³H]-thymidine incorporation after 24 hours. Each point was made in triplicate, and the values represented correspond to the mean ± SD of 3 independent experiments.