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 Spark NIR 685
Spark NIR® 685 from Biolegend is a fluorophore designed for spectral flow cytometry with an excitation peak at 633 nm and an emission peak at 685 nm. This fluorophore is an alternative to Alexa Fluor™ 660 and can be efficiently excited by the 633 nm laser and can be unmixed from Alexa Fluor™ 647 and Alexa Fluor™ 700.