|Detection of CD8 in Cotton Rat Splenocytes by Flow Cytometry. Cotton rat splenocytes were stained with Sheep Anti-Cotton Rat CD8 alpha Antigen Affinity-purified Polyclonal Antibody (Catalog # AF7080, filled histogram) or control antibody (Catalog # 5-001-A, open histogram), followed by Allophycocyanin-conjugated Anti-Sheep IgG Secondary Antibody (Catalog # F0127).|
CD8 alpha (CD8 alpha ; also OX8, Leu-2 and Lyt-2) is a 23 kDa (predicted) member of the Ig superfamily of molecules. It is found on immature thymocytes, cytotoxic and suppressor T cells, select mast cells, and splenic plus bone marrow dendritic cells (in rodent). On T cells, CD8 alpha exists as either a disulfide linked homodimer, or heterodimer bound to CD8 beta. CD8 alpha beta is best known as a coreceptor for the TCR, enhancing TCR signaling. CD8 alpha alpha serves a different function and acts as a TCR corepressor that blocks T cell activation. Based on rat, mature Sigmodon hispidus/cotton rat CD8 alpha is a 210 amino acid (aa) type I transmembrane protein. It will possess a 161 aa extracellular region (aa 24-184) that contains one V-type Ig-like domain (aa 35-135), and a 30 aa cytoplasmic tail (aa 206-235). Although Sigmodon hispidus is called a rat, it is not. It is a rodent, and rat CD8 alpha is the closest ortholog to cotton rat CD8 alpha currently reported. Over the extracellular region, rat and cotton rat CD8 alpha share only 54% aa identity. Rat CD8 alpha runs at 34-39 kDa in SDS‑PAGE, and possesses one utilized N-linked and O-linked glycosylation site (vs. no N-linked sites in cotton rat CD8 alpha ). Based on this organization, and assuming O-linked glycosylation, cotton rat CD8 alpha would be expected to run at about 30-34 kDa in SDS‑PAGE. Over aa 24-182, cotton rat CD8 alpha shares 54% and 48% aa identity with rat and mouse CD8 alpha, respectively.