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 CF405S
CF®405S from Biotium is a fluorophore with an excitation peak at 404 nm and an emission peak at 431 nm. It is spectrally similar to Alexa Fluor™ 405. It can be use in fluorescence microscopy, specifically its been validated in Structured Illumination (SIM), and flow cytometry. However, in flow cytometry, superior alternatives are Brilliant™ Violet 421, SuperNova v428 and StarBright Violet 440.