The 1-1-2 monoclonal antibody specifically recognizes the Qa-2 MHC class Ib antigen, which is expressed at higher levels on mature T lymphocytes than on B cells. Its expression is upregulated in the late stages of T-cell maturation. Qa-2 is a 40 kDa GPI-linked cell surface molecule encoded by the Q5, Q6, Q7, and/or Q9 genes of the H-2 complex. A 39 kDa soluble form results from alternative splicing of the transcript. Although Qa-2 is nonpolymorphic, its level of expression on both T and B lymphocytes varies among inbred mouse strains. High expressors include strains carrying the H-2[b] haplotype low expressors include H-2[d] strains, and H-2[k] strains are Qa-2-negative.
The antibody was conjugated to BD Horizon™ BUV563 which is part of the BD Horizon Brilliant™ Ultraviolet family of dyes. This dye is a tandem fluorochrome of BD Horizon BUV395 which has an Ex Max of 348 nm and an acceptor dye. The tandem has an Em Max at 563 nm. BD Horizon BUV563 can be excited by the 355 nm ultraviolet laser. On instruments with a 561 nm Yellow-Green laser, the recommended bandpass filter is 585/15 nm with a 535 nm long pass to minimize laser light leakage. When BD Horizon BUV563 is used with an instrument that does not have a 561 nm laser, a 560/40 nm filter with a 535 nm long pass may be more optimal. Due to the excitation and emission characteristics of the acceptor dye, there may be spillover into the PE and PE-CF594 detectors. However, the spillover can be corrected through compensation as with any other dye combination.