The 87G monoclonal antibody specifically recognizes Human Leukocyte Antigen G (HLA-G) which is encoded by HLA-G (major histocompatibility complex, class I, G). HLA-G is a nonclassical Major Histocompatibility Complex class I (MHC-Ib) molecule that is structurally related to the classical MHC class Ia antigens (HLA-A, -B, -C). Several HLA-G isoforms have been described including transmembrane HLA-G1, -G2, -G3, -G4 and soluble HLA-G5, -G6, and -G7. The 87G monoclonal antibody reportedly recognizes a conformationally-dependent epitope on the heterodimeric transmembrane HLA-G1 and soluble HLA-G7 isoforms that consist of an HLA-G alpha chain and β2-microglobulin (β2m). HLA-G1 is variably expressed on placental trophoblast cells, thymic epithelial cells, activated monocytes, macrophages, dendritic cells, and tumor cells. Heterodimeric HLA-G shows limited variation and binds a limited variety of self-peptides derived from intracellular proteins including histones and ribosomal proteins. This molecule binds to inhibitory receptors such as CD85d, CD85j, and CD158d that are differentially expressed by NK cells, T cells, monocytes, dendritic cells, and B cells. This interaction exerts suppressive regulation of immune responses and is thought to help safeguard maternal tolerance of the fetus during pregnancy. The 4H84 monoclonal antibody that reportedly recognizes denatured forms of HLA-G1 and HLA-G2 has also been described.
The antibody was conjugated to BD Horizon™ BUV496 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 496-nm. BD Horizon BUV496 can be excited by the ultraviolet laser (355 nm) and detected with a 515/30 nm filter with a 450LP. Due to the excitation of the acceptor dye by other laser lines, there may be significant spillover into the channel detecting BD Horizon V500 or BV510 (eg, 525/40-nm filter). However, the spillover can be corrected through compensation as with any other dye combination.