About CD4
This gene encodes the CD4 membrane glycoprotein of T lymphocytes. The CD4 antigen acts as a coreceptor with the T-cell receptor on the T lymphocyte to recognize antigens displayed by an antigen presenting cell in the context of class II MHC molecules. The CD4 antigen is also a primary receptor for entry of the human immunodeficiency virus through interactions with the HIV Env gp120 subunit. This gene is expressed not only in T lymphocytes, but also in B cells, macrophages, granulocytes, as well as in various regions of the brain. The protein functions to initiate or augment the early phase of T-cell activation, and may function as an important mediator of indirect neuronal damage in infectious and immune-mediated diseases of the central nervous system. Multiple alternatively spliced transcript variants encoding different isoforms have been identified in this gene. [provided by RefSeq, May 2020]

About APC-eFluor 780
APC-eFluor™ 780 (APC-eF780) is a red-emitting tandem fluorophore of APC, excited by the 640 nm red laser and transfers energy to the acceptor, eF780, which emits light that can be captured with a 780/60 nm bandpass filter. APC-eF780 has an excitation peak at 645 nm and an emission peak at 767 nm, and is spectrally similar to APC-CF®750 (Biotium), APC-Cy® 7 (GE Healthcare) APC-H7 (BD Biosciences), APC-eFluor™ 780 (ThermoFisher Scientific), APC-Vio®770 (Miltenyi Biotec) and APC-Fire™ 750 (BioLegend). This dye is part of the larger eFluor™ dye family, developed by eBioscience which is now part of ThermoFisher Scientific.