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 Blue 515
Spark Blue™ 515 exhibits peak excitation/emission wavelengths at 506 nm and 516 nm respectively, most closely matching the spectra of cFluor® B515. On conventional cytometers, it can be detected with a 488 nm blue laser and the 530/30 filter set typically used by FITC or Alexa Fluor® 488. On spectral instruments with the proper settings, it is possible to unmix Spark Blue™ 515 from dyes like FITC, Alexa Fluor® 488, and KIRAVIA Blue 520™ as its peak emission is shifted over 10 nm. With a dim brightness, Spark Blue™ 515 is best suited for detecting antigens with medium to high expression levels. It is also stable towards exposure to heat or a variety of commonly used fixative solutions.