Cystatin A, also known as stefin A, is a member of the cystatin superfamily of cysteine protease inhibitors. It primarily regulates the activity of cysteine proteases, such as cathepsins B, H, and L, by blocking their enzymatic function, thereby maintaining protease-antiprotease balance in tissues. This 11 kDa intracellular protein is expressed in various epithelial and immune cells, playing roles in cell proliferation, differentiation, apoptosis, and immune modulation. Dysregulation of cystatin A has been implicated in pathological conditions, including cancer, neurodegenerative disorders, and inflammatory diseases, where uncontrolled protease activity contributes to tissue damage or disease progression.
Antibodies targeting cystatin A are essential tools for investigating its biological functions and clinical relevance. They enable the detection and quantification of cystatin A expression in tissues and bodily fluids using techniques like Western blotting, immunohistochemistry, and ELISA. These antibodies have been employed to study its downregulation in certain cancers (e.g., squamous cell carcinoma) or accumulation in amyloid deposits in neurodegenerative conditions. Both monoclonal and polyclonal anti-cystatin A antibodies are available, with specific applications depending on required sensitivity and experimental design. Recent research also explores their potential diagnostic utility, particularly in cancer biomarker panels or inflammatory disease monitoring. However, interpretation requires caution due to cross-reactivity risks with homologous cystatin family members in some antibody preparations.