About PD-1
Programmed cell death protein 1 (PDCD1) is an immune-inhibitory receptor expressed in activated T cells; it is involved in the regulation of T-cell functions, including those of effector CD8+ T cells. In addition, this protein can also promote the differentiation of CD4+ T cells into T regulatory cells. PDCD1 is expressed in many types of tumors including melanomas, and has demonstrated to play a role in anti-tumor immunity. Moreover, this protein has been shown to be involved in safeguarding against autoimmunity, however, it can also contribute to the inhibition of effective anti-tumor and anti-microbial immunity. [provided by RefSeq, Aug 2020]

About Brilliant Ultraviolet 661
Brilliant™ UltraViolet 661 (BUV661) is a red-emitting tandem fluorophore that combines BD Horizon® BUV395 and an acceptor dye. It can be excited by the 355 nm ultraViolet laser and collected using a 670/25 bandpass filter. BUV661 has an excitation peak at 498 nm and an emission peak at 657 nm BUV661 has a medium/high relative brightness, and is most commonly used for multicolor flow cytometry. This dye is part of the Brilliant™ UltraViolet dye family, developed and sold by BD Biosciences. This family of dyes uses BUV396 as the donor so that all dyes in the family can be excited by the 355 nm ultraViolet laser. Depending on the acceptor, the dyes in this family have different relative brightness ratings.