A method for measuring the protease activity of a convertase of the alternative complement pathway is provided. The method typically comprises immobilizing a biotinylated C3b on a solid phase coated with a biotin binding protein. Substantially homogeneous components of the alternative complement pathway may be incubated with the immobilized C3b in a serum free and a gelatin free buffer, to form a convertase. The activity of the convertase is generally measured with an immunoassay.

Provided herein are methods to identify agents or compounds that specifically modulate the oligomerization and/or functional activities of receptor protein tyrosine phosphatase sigma (RPTP) in an abnormal fibroblast cell and therapies based therefrom.

A method for measuring the protease activity of a convertase of the alternative complement pathway is provided. The method typically comprises immobilizing a biotinylated C3b on a solid phase coated with a biotin binding protein. Substantially homogeneous components of the alternative complement pathway may be incubated with the immobilized C3b in a serum free and gelatin free buffer, to form a convertase. The activity of the convertase is generally measured with an immunoassay.