The 3D12 monoclonal antibody specifically recognizes Human Leukocyte Antigen E (HLA-E) that is widely expressed on leucocytes and some other cell types. Cell surface HLA-E is normally expressed as a noncovalent complex comprised of the ~45 kDa type I transmembrane, HLA-E heavy-chain glycoprotein, the ~12 kDa invariant β2-microglobulin (β2m) light chain, and a short bound peptide. Human HLA-E represents a nonclassical Major Histocompatibility Complex class I (MHC class Ib) molecule that is homologous to mouse H-2 Qa-1. Although structurally related to the classical, highly polymorphic MHC class Ia antigens (HLA-A, -B, -C), HLA-E shows limited polymorphism. HLA-E functions in the regulation or self-nonself discrimination of innate and adaptive immune responses. In addition to binding self peptides, the HLA-E complex can selectively bind and present peptides derived from bacterial or viral pathogen-infected cells, stressed cells, or tumor cells to elicit antigen-specific, HLA-E-restricted CD8+ T cell responses. The cell surface HLA-E complex likewise serves as a ligand for heterodimeric CD94:NKG2A inhibitory and CD94:NKG2C activating receptors that are differentially expressed on NK cells and some T cells. These ligand:receptor interactions can either suppress or promote NK or T cell-mediated responses. The 3D12 antibody reportedly binds to both free or complexed HLA-E heavy chain and can block HLA-E-dependent function.
The antibody was conjugated to BD Horizon™ BV650 which is part of the BD Horizon Brilliant™ Violet family of dyes. This dye is a tandem fluorochrome of BD Horizon BV421 with an Ex Max of 405-nm and an acceptor dye with an Em Max at 650-nm. BD Horizon BV650 can be excited by the violet laser and detected in a filter used to detect APC-like dyes (eg, 660/20-nm filter). Due to the excitation and emission characteristics of the acceptor dye, there will be spillover into the APC and Alexa Fluor® 700 detectors. However, the spillover can be corrected through compensation as with any other dye combination.