The KT50 antibody reacts with some members of the Vα 8 T-cell Receptor (TCR) subfamily of mice having the a, b, c, and d haplotypes of the Tcra gene complex (e.g., all strains tested). It recognizes an epitope in the CDR1 of Vα 8.3, but not Vα 8.2, TCR subfamily member, as does the B21.14 mAb (Cat. no. 553374). Site-directed mutagenesis has identified three amino acids which are necessary for antibody reactivity and which are unique to Vα 8.3 among the five functional Vα 8 TCR subfamily members. On a common H-2[k] background, the frequency of Vα 8.3 TCR-bearing T lymphocytes is higher in Tcra[a/a] mice than in Tcra[a/b] mice. Furthermore, studies of congenic strains suggest that CD8+ Vα 8.3 TCR-bearing T lymphocytes undergo negative selection in mice expressing MHC class I antigens of the H-2[d] haplotype.
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.