The XBP1 (X-box binding protein 1) antibody is a critical tool for studying the unfolded protein response (UPR), a cellular stress mechanism activated during endoplasmic reticulum (ER) dysfunction. XBP1. a transcription factor, exists in two isoforms: unspliced XBP1 (XBP1u) and spliced XBP1 (XBP1s). Under ER stress, the endoribonuclease IRE1α cleaves XBP1u mRNA, removing a 26-nucleotide intron and producing XBP1s, which regulates genes involved in protein folding, ER-associated degradation (ERAD), and lipid biosynthesis. Antibodies targeting XBP1 distinguish between these isoforms, enabling researchers to assess UPR activation in diseases like cancer, neurodegenerative disorders, and metabolic conditions. For example, XBP1s is linked to tumor survival in multiple myeloma and drug resistance in solid cancers. In neurodegenerative contexts, XBP1 dysregulation correlates with protein misfolding in Alzheimer’s and Parkinson’s diseases. Commercial XBP1 antibodies are typically monoclonal or polyclonal, validated for techniques such as Western blotting, immunofluorescence, and immunohistochemistry. Specific clones (e.g., anti-XBP1s) are optimized to detect the active isoform, while others recognize both forms. Robust validation, including knockout controls, ensures specificity. These antibodies are pivotal for dissecting UPR pathways and exploring therapeutic strategies targeting XBP1 in disease models.