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 PerCP-Cy5.5
PerCP-Cyanine® 5.5 (PerCP-Cy5.5) is a red-emitting tandem fluorophore that was originally designed to make the PerCP fluorophore more stable and increase signal intensity. The donor molecule, PerCP can be excited by the 488-nm blue laser and and transfers energy to the acceptor molecule, Cy5.5, which emitts light that can be captured with a 695/40 nm bandpass filter. PerCP-Cy5.5 has an excitation peak at 482 nm and an emission peak at 695 nm. There are superior alternatives to PerCP and PerCP-Cy5.5 including BB700, NovaFluor Blue 690 or PerCP-eFluor™ 710