The M1/42 monoclonal antibody (mAb) specifically recognizes intact Histocompatibility-2 Region (H-2) class I antigens (Ags), also known as mouse Major Histocompatibility Complex class I (MHC-I) Ags. This mAb reportedly binds to one or more of the H-2 Ags (H-2K, H-2D, and likely H-2L) that are primarily expressed on most nucleated somatic cells of hematopoietic and nonhematopoietic origin. H-2 class I molecules are comprised of a ~45-50 kDa type I transmembrane heavy chain glycoprotein that is noncovalently linked to ~13 kDa β2-microglobulin (β2-m). The extracellular region of the polymorphic heavy chains is comprised of three globular domains (α1, α2, and α3), followed by a transmembrane region and a cytoplasmic tail. Sequence variations are manifest in regions of the α1 and α2 domains that line the peptide-binding cleft involved in Ag presentation. The M1/42 mAb reportedly binds to H-2 class I Ags from multiple mouse haplotypes including a, b, d, j, k, s, and u. It does not bind to separated H-2 class I heavy chains or β2-m. Cell surface CD8 molecules bind to invariant sites of the H-2 heavy chains and can provide coreceptor signaling for Ag-mediated activation through the T cell receptor. H-2 class I molecules that present self-Ags can lead to self-tolerance of maturing CD8+ T cells due to thymic selection. Alternatively, these molecules can present foreign peptide Ags to mature peripheral CD8+ T cells resulting in cell-mediated immune responses against foreign Ags. H-2 class I Ags also serve as ligands for activating and inhibitory receptors expressed by NK cells and some T cells. The M1/42 antibody is useful for analyzing H-2 class I Ag expression on cells or cell lines. Cells from different experimental systems, eg, stressed cells that have undergone infection or transformation, may express little or no H-2 class I Ag. In contrast, cells undergoing activation or responding to certain factors (eg, interferons) may express upregulated levels of these Ags.
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.