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 PE-eFluor 610
PE-eFluor™ 610 (PE-eF610, RPE-eF610) from Thermo Fisher Scientific is an orange-emitting tandem fluorophore that combines pycoerythrin (PE) and eFluor™ 610. The donor molecule, PE can be excited by the 488-nm blue, 532-nm green, or 561-nm yellow-green laser and and transfers energy to the acceptor molecule, eF610, which emitts light that can be captured with a 610/20 nm bandpass filter. PE-eF610 has an excitation peak at 565 nm and an emission peak at 607 nm, and is suitable alternative to PE-Texas Red®. PE-eF610 is mainly used for flow cytometry. This tandem is often a great option because of PE is excitable by multiple lasers due to its broad excitation spectrum and the eFluor™ 610 acceptor molecule emits brightly in the Orange/Red spectrum. Many cytometers are commonly set up with the 610/20 bandpass filter that can detect this fluorophore's emission. This dye is part of the larger eFluor™ dye family, developed by eBioscience which is now part of ThermoFisher Scientific.