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™ BUV496 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 with an Ex Max of 348-nm and an acceptor dye with an Em Max at 496-nm. BD Horizon BUV496 can be excited by the ultraviolet laser (355 nm) and detected with a 515/30 nm filter with a 450LP. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into the channel detecting BD Horizon V500 or BV510 (eg, 525/40-nm filter). However, the spillover can be corrected through compensation as with any other dye combination.