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CD8α is a crucial subunit of the CD8 co-receptor complex found on the surface of cytotoxic T lymphocytes （CTLs） and some natural killer （NK） cells. It is a 32 kDa glycoprotein that can form either an α/β heterodimer or an α/α homodimer with CD8β. CD8α plays a vital role in immune responses by binding to MHC class I molecules on antigen-presenting cells （APCs）, facilitating the recognition and destruction of infected or abnormal cells. This interaction helps activate the T cell receptor （TCR） complex, recruiting the LCK kinase and initiating multiple signaling pathways. Additionally, CD8αα homodimers are found on intraepithelial lymphocytes （IELs）, which protect mucosal surfaces like the intestinal barrier.