The purpose of this study is to evaluate serum soluble human Suppression of Tumorigenicity 2 (ST2) protein, the receptor for IL-33 and a member of the proinflammatory IL-1 receptor superfamily, as a surrogate biological marker predictive of disease outcome and therapeutic response to golimumab treatment in subjects with moderate to severe UC who have failed on prior conventional therapies. The primary endpoints of this study are to correlate serum soluble ST2 levels with endoscopic activity (endoscopic subscore of the Mayo score) and histological activity (Geboes index) of disease.