Anti-AREI antibodies are used in antigen-specific immunodetection in biological samples. The target AREI is a known alias name of the protein cystatin A, encoded by the CSTA gene in humans. This 98-amino acid residue protein is an intracellular thiol proteinase inhibitor. It is localized to the cytoplasm of the cell. In terms of tissue expression, it is reported to be expressed in the skin throughout the epidermis. The term PSS4 is another synonym for AREI.