Detection of CD6 in Human Whole Blood Lymphocytes by Flow Cytometry. Human whole blood lymphocytes were stained with Goat Anti-Human CD6 Alexa Fluor® 488‑conjugated Antigen Affinity-purified Polyclonal Antibody (Catalog # FAB627G, filled histogram) or isotype control antibody (Catalog # IC108G, open histogram). View our protocol for Staining Membrane-associated Proteins.
Preparation and Storage
The product is shipped with polar packs. Upon receipt, store it immediately at the temperature recommended below.
Stability & Storage
Protect from light. Do not freeze.
12 months from date of receipt, 2 to 8 °C as supplied.
Human CD6 is a 105 kDa (unphosphorylated) -130 kDa
(hyperphosphorylated) glycoprotein Group B member of the SRCR (Scavenger
Receptor Cys-Rich) superfamily of molecules.
It has a restricted expression pattern, being limited to select CD56dim
NK cells, B1a B cells (IgM producers), thymocytes and virtually all resting T
cells. Mature CD6 is a type I
transmembrane protein 651 amino acids (aa) in length. It contains a 385 aa extracellular region (aa
19-402) that possesses three SRCR repeats, and a relatively long 245 aa
cytoplasmic domain. There are at least
six alternative splice forms for human CD6, four of which (plus the full-length
form) contain an unspliced extracellular region. The isoform used here for immunization
(SwissProt: Q8WWJ7) is one of these four, showing splicing only in the
cytoplasmic region. Thus, the polyclonal
antibody used here will recognize all full-length CD6 molecules, and may, by an
absence of staining, suggest the presence of the two isoform variants that are
missing the third SRCR repeat that lies between aa 259-361. CD6 has multiple interaction partners. It complexes with CD5 in cis, contributing to the immunological synapse; in trans, it binds to dendritic cell CD166/ALCAM
on the surface of adjacent cells. CD6 is
also known to bind soluble galectin-1 and -3, and to bind the PAMPs associated
with pathogenic microbes. Notably, on T cells and following activation,
full-length CD6 is downregulated, and a splice variant lacking the third SRCR
is upregulated, abrogating any CD6:CD166 interaction. Functions attributed to CD6 include the
induction of chemokine secretion by NK cells, costimulation of antigen
recognition by T cells, and an antimicrobial activity attributed to an 85 kDa
soluble form of CD6. Over aa 18-398,
human and mouse CD6 share 68% aa sequence identity.
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