The 5H10-1 monoclonal antibody specifically recognizes CD8a which is also known as CD8 alpha (CD8α), Ly-2 or Lyt-2. CD8a is an ~34 kDa single pass type I transmembrane glycoprotein that is encoded by Cd8a (CD8 antigen, alpha chain) which belongs to the immunoglobulin superfamily (IgSF). CD8a is comprised of an extracellular region that contains an IgV-like domain followed by a transmembrane region and cytoplasmic tail with a Lck tyrosine kinase binding motif. CD8a is expressed on the cell surface as either a disulfide bond-linked homodimer (CD8αα) or a heterodimer (CD8αβ) when disulfide bonded to CD8b (also known as, CD8 beta/CDβ, Ly-3, or Lyt-3), another type I transmembrane glycoprotein. CD8aβ is expressed on most thymocytes and a subpopulation of mature peripheral TCR αβ T cells including some intraepithelial lymphocytes (IELs). CD8αα is expressed on IELs which include either TCR αβ or TCR γδ T cells as well as on other leucocytes, such as, subsets of NK cells and dendritic cells (DCs). CD8αβ serves as a co-receptor for antigen-stimulated CD8+ T cells by binding to the same peptide:MHC class I complex as the T cell receptor and by helping to trigger the subsequent signaling cascade through Lck activation upon antigen recognition. Through high-affinity binding to nonclassical MHC class-Ib molecules, CD8αα can reportedly function less efficiently as a co-receptor and even repress antigen-stimulated CD8+ T cell responses.
The antibody was conjugated to BD Horizon™ BUV805 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 with an Ex Max of 348 nm and an acceptor dye with an Em Max at 805 nm. BD Horizon Brilliant BUV805 can be excited by the ultraviolet laser (355 nm) and detected with a 820/60 filter and a 770LP.