The TMEM121B (Transmembrane Protein 121B) antibody is a tool used to study the function and localization of the TMEM121B protein, a relatively undercharacterized member of the transmembrane protein family. TMEM121B is predicted to contain multiple transmembrane domains, suggesting roles in membrane-associated processes such as ion transport, cell signaling, or organelle organization. While its exact biological functions remain unclear, recent studies link TMEM121B to cellular stress responses and neurodegenerative diseases. For example, it has been identified as a potential interactor of proteins involved in autophagy and lysosomal regulation. The antibody, typically developed in rabbit or mouse hosts, enables detection of TMEM121B in techniques like Western blotting, immunofluorescence, and immunohistochemistry. Commercial versions are often validated for specificity using knockout cell lines or tissues. Research applications focus on exploring TMEM121B's expression patterns across tissues, its subcellular localization (particularly in endoplasmic reticulum or Golgi compartments), and its potential involvement in pathological conditions like cancer or Alzheimer’s disease. Challenges include limited functional data and the need for further validation of antibody performance across experimental models. Ongoing work aims to clarify TMEM121B's role in membrane dynamics and disease mechanisms.