The L120 monoclonal antibody specifically recognizes CD4. CD4 is an ~59 kDa type I transmembrane glycoprotein that belongs to the Ig gene superfamily. CD4 is expressed on helper-inducer subset of T lymphocytes and monocytes. The CD4 antigen is involved in the Major Histocompatibility Complex (MHC) class II-restricted recognition of foreign antigens and has been identified as a receptor for HIV. The L120 antibody recognizes amino acids 306-370 of the antigen and does not block the binding of the gp120 of HIV, but inhibits the proliferation of CD4 T lymphocytes to MHC class II antigens. The CD4 antigen is present on most thymocytes, approximately 40% of peripheral blood lymphocytes, and at lower density on monocytes. Peripheral blood CD4+ T lymphocytes are lost over time during HIV infection, and this loss is correlated with disease progression.
The antibody was conjugated to BD Horizon™ BV786 which is part of the BD Horizon Brilliant™ Violet family of dyes. This dye is a tandem fluorochrome of BD Horizon BV421 with an Ex Max of 405-nm and an acceptor dye with an Em Max at 786-nm. BD Horizon BV786 can be excited by the violet laser and detected in a filter used to detect Cy™7-like dyes (eg, 780/60-nm filter).