Figure 1.

Identification of monoclonal antibodies to hFSTL3 with neutralizing activity. Monoclonal antibodies to hFSTL3 were screened for ability to neutralize hFSTL3 binding to activin, which releases bioactive activin from inhibition by FSTL3. This activin was quantified using HEK293 cells stably expressing the CAGA-Luc activin reporter as previously described (20). Signaling by activin alone is shown in the brown bar and inhibition by FSTL3 shown in green. Increasing concentrations of FP-101 (red) neutralize the ability of FSTL3 to bind activin as demonstrated by increasing activin bioactivity. FP-102 and 103 were less active. A non-neutralizing monoclonal antibody was used as an immunoglobulin control. Shown is mean of 3 experiments.