The CRCBT-02-001 monoclonal antibody specifically binds to human CD364 which is also known as Peptidase inhibitor 16 (PI-16) or Protease inhibitor 16. PI-16 is a glycophosphatidylinositol-linked, 436 amino acid surface glycoprotein. It is a member of the cysteine-rich secretory protein (CRISP) family and is likewise known as CRISP9. PI-16 is a putative serine protease inhibitor and can serve as a binding protein for PSP94 (prostate secretory protein of 94 amino acids) termed PSPBP. Serum levels of PSP94 and PI-16 can reportedly serve as key targets for prostate cancer research. PI-16 is highly expressed by the activated/memory, FoxP3-bright subsets of regulatory T cells. PI-16-positive regulatory T cells expressed uniformly high levels of the chemokine receptors, CCR4 and CCR6, when compared with PI-16-negative T regulatory cells. The results suggest that the CCR4+CCR6+ regulatory T cells are capable of homing to inflammatory sites and regulating effector T cells such as CCR4+CCR6+ Th17-like cells. PI-16 is also expressed by subsets of memory CD4+ and CD8-bright T cells. It is not expressed by B cells or monocytes.
The antibody was conjugated to BD Horizon™ BUV661 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 with an Ex Max of 348-nm and an acceptor dye with an Em Max at 661-nm. BD Horizon Brilliant BUV661 can be excited by the ultraviolet laser (355 nm) and detected with a 670/25 filter and a 630 nm LP. Due to cross laser excitation of this dye, there may be significant spillover into channels detecting APC-like emissions (eg, 670/25-nm filter).
Due to spectral differences between labeled cells and beads, using BD™ CompBeads can result in incorrect spillover values when used with BD Horizon BUV661 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV661 reagents (eg, CD4 vs. CD45) can have slightly different fluorescence spillover therefore, it may also be necessary to use clone-specific compensation controls when using these reagents.