SCD4, Recombinant, Cotton Rat (Stearoyl-CoA Desaturase 5, Acyl-CoA-desaturase 4, HSCD5, Stearoyl-CoA 9-desaturase, SCD5, ACOD4)

CD4, also known as L3T4, T4, and W3/25, is an ~55kD type I transmembrane glycoprotein that is expressed predominantly on thymocytes and a subset of mature T lymphocytes. It is a standard phenotype marker for the identification of T cell populations (1). CD4 contains four immunoglobulin-like domains in its extracellular region. Within the ECD, human CD4 shares ~52% aa sequence identity with mouse and rat CD4, while mouse and rat CD4 share 73% identity. CD4 is expressed along with CD8 on double positive T cells during their development in the thymus. Either CD4 or CD8 expression is then lost, giving rise to single positive (SP) CD4+ or CD8+ mature T cells (2). CD4+ SP cells, also known as T helper cells, further differentiate into multiple subsets of CD4+ cells including Th1, Th2, Th17, Tfh, and Treg cells which regulate humoral and cellular immunity (3). CD4 is re-expressed on circulating CD8+ T cells upon activation and contributes to their cytotoxic effector activity (4). In human, CD4 is additionally expressed on macrophages, neutrophils, monocytes, NK cells, and neurons and glial cells in the brain (5-8). Similar CD4 distribution between species cannot be assumed as demonstrated by its presence on macrophages in human and rat but not in mouse (5). CD4 binds directly to MHC class II molecules on antigen presenting cells (9). This interaction contributes to the formation of the immunological synapse which is focused around the TCR-MHC class II-antigenic peptide interaction (1, 10). Palmitoylation of two cysteine residues in the cytoplasmic tail of CD4 promotes the localization of CD4 in lipid rafts and its ability to augment TCR signaling via activation of the tyrosine kinase Lck (11). CD4 also functions as a chemotactic receptor for IL-16 and, in human, as a coreceptor for the gp120 surface glycoprotein of HIV-1 (6, 12-14). CD4 associates with adhesion molecule CD44 at the cell surface, and triggers CD44-mediated cell adhesion (15).\n\nSource:\nRecombinant corresponding to aa1-393 of rat sCD4 (CFS), fused with 6-His tag at C-terminal, expressed in mouse myeloma cell line, NS0.\n\nMolecular Weight: \n~42.4kD\n\nEndotoxin Level:\n(same/less than)1EU/1ug (LAL)\n\nBiological Activity:\nMeasured by the ability of the immobilized protein to support the adhesion of NIH/3T3 mouse embryonic fibroblasts (ATCC: CRL-1685). The ED50 for this effect is typically 0.2-1ug/ml after a 1 hour incubation at 37 degrees C.\n\nStorage and Stability:\nLyophilized powder may be stored at -20 degrees C. Stable for 12 months at -20 degrees C. Reconstitute with PBS. Aliquot to avoid repeated freezing and thawing. Store at -20 degrees C. Reconstituted product is stable for 6 months at -20 degrees C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.

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