The K10.6 monoclonal antibody specifically recognizes Lyb-2.1, Lyb-2.2, and Lyb-2.4 (CD72 a, b, and d alloantigens, respectively). CD72 is a 45-kDa type-II membrane protein, containing a C-type lectin-like domain and ITIM and ITIM-like sequences in the cytoplasmic tail. CD72 is expressed at all stages of B-lymphocyte development except plasma cells, and it has been shown to negatively regulate B-cell receptor signaling. Analysis of CD72-deficient mice supports these results and shows that CD72 is involved in B-cell development. CD72-stimulated B cells show a transient association of CD19 with CD72, as well as an increase in Tyr-phosphorylation of CD19. CD72 is reported to be a ligand for CD5, although this is controversial. It is also reported to be a ligand for CD100 (Sema4D). The CD72 alloantigens Lyb-2.1 (originally identified as Ly-m19.2), Lyb-2.2 (originally identified as Ly-32.2), Lyb-2.3, and Lyb-2.4 are encoded by the Cd72[a], Cd72[b], Cd72[c], and Cd72[d] alleles, respectively. Lyb-2.1 is expressed on B lymphocytes of CBA/J, C3H/Bi, C57BR, C57L, C58, DBA/1, DBA/2, and SWR strains. Lyb-2.2 is expressed on B lymphocytes, a subset of peripheral T cells, and activated T lymphocytes in A, BALB/c, CBA/H, C3H/He, C57BL, PL, and 129 strains. Lyb-2.4 is expressed on a subset of splenocytes of the STS/A strain. K10.6 antibody does not react with Lyb-2.3 (AKR and SJL strains) nor with non-lymphoid tissues. Five serological specificities of CD72 alloantigens have been described and the nomenclature CD72.1, CD72.2, CD72.3, CD72.4, and CD72.5 proposed, which does not correspond to the names of the alleles. Some authors have referred to the specificity of mAb K10.6 as CD72.4.
This antibody is conjugated to BD Horizon™ BV605 which is part of the BD Horizon Brilliant™ Violet family of dyes. With an Ex Max of 407-nm and Em Max of 602-nm, BD Horizon BV605 can be excited by a violet laser and detected with a standard 610/20-nm filter set. BD Horizon BV605 is a tandem fluorochrome of BD Horizon BV421 and an acceptor dye with an Em max at 605-nm. Due to the excitation of the acceptor dye by the green (532 nm) and yellow-green (561 nm) lasers, there will be significant spillover into the PE and BD Horizon PE-CF594 detectors off the green or yellow-green lasers. BD Horizon BV605 conjugates are very bright, often exhibiting brightness equivalent to PE conjugates and can be used as a third color off of the violet laser.