The SK3 monoclonal antibody specifically binds to CD4. The CD4 antigen is a 55 kDa type 1 transmembrane glycoprotein that belongs to the immunoglobulin superfamily. It is expressed on T-helper/inducer lymphocytes and monocytes. CD3+CD4+ T cells comprise approximately 28% to 58% of normal peripheral blood lymphocytes. CD4 is also expressed on 80% to 95% of normal thymocytes. The CD4 antigen is present in low density on the cell surface of monocytes and in the cytoplasm of monocytes and macrophages (CD3-CD4+). CD4 serves as a T cell coreceptor for MHC class II antigen recognition and as a receptor for the human immunodeficiency virus (HIV). The SK3 antibody inhibits HIV binding to CD4+ cells.
The antibody was conjugated to BD Horizon Red 718, which has been developed exclusively for BD Biosciences as a better alternative to Alexa Fluor® 700. BD Horizon Red 718 can be excited by the red laser (628 – 640 nm) and, with an Em Max around 718 nm, it can be detected using a 730/45 nm filter. Due to similar excitation and emission properties, we do not recommend using R718 in combination with APC-R700 or Alexa Fluor® 700.