Anti-Hu CD4, RPA-T4, FI, 25tests

This FITC-conjugated monoclonal antibody, supplied by STEMCELL Technologies as a mouse IgG1, kappa reagent (clone RPA-T4), targets CD4 on human and chimpanzee cells. CD4 is an ~59 kDa single-chain type 1 transmembrane glycoprotein and member of the immunoglobulin (Ig) superfamily, containing four extracellular Ig-like domains (D1–D4). The epitope recognised by clone RPA-T4 maps to the D1 domain, which structurally resembles an Ig variable domain. CD4 is expressed at relatively high levels by most thymocytes and by a subpopulation of T cells (T helper cells), and at lower levels by peripheral blood monocytes and macrophages.

The antibody was raised in a BALB/c mouse against phytohemagglutinin (PHA)-stimulated human peripheral blood mononuclear cells (PBMCs), purified by affinity chromatography and conjugated with FITC, and is formulated in phosphate-buffered saline (pH 7.2) containing 0.09% sodium azide, 0.1% gelatin, and <0.2% (w/v) bovine serum albumin. Applications are verified and reported for flow cytometry, and the clone is cited in functional and blocking studies. Binding blocks HIV attachment and the mixed lymphocyte reaction (MLR), inhibits in vitro activation of CD4+ T cells by interfering with the CD4–HLA-DR interaction, and partially blocks binding of antibody clone SK3; the epitope is reportedly sensitive to formaldehyde fixation. The reagent is supplied as a clear liquid that is not classified as hazardous under GHS. For flow cytometry the manufacturer suggests ≤ 5 μL per 1 × 10^6 cells in 100 μL, with titration recommended for optimal performance, and the product should be stored at 2 – 8 °C undiluted, protected from prolonged exposure to light and not frozen.