Used in research and diagnostic applications to detect and quantify Cathepsin S, a lysosomal cysteine protease involved in antigen processing and presentation. Plays a key role in studying autoimmune diseases, cancer, and inflammatory conditions where Cathepsin S activity is dysregulated. Enables immunohistochemistry, Western blotting, and ELISA assays to assess protein expression levels and localization in tissues and cells. Supports drug development efforts targeting Cathepsin S inhibition by providing a reliable tool for monitoring target engagement and biological response.