The MIH43 monoclonal antibody specifically binds to human B7-H4 (B7 family member, H4) that is encoded by the VTCN1 (V-set domain containing T cell activation inhibitor 1) gene. B7-H4 is a type I membrane glycoprotein with a calculated molecular weight of 30.89 kDa. It is also known as VCTN1, B7h.5, B7S1 (B7 superfamily member 1) or B7X. B7-H4 is a newly discovered member of the B7 family of costimulatory proteins. B7-H4 is not constitutively expressed on peripheral tissues. Its expression can be induced on macrophages, dendritic cells, B cells and T cells. By binding to its putative receptor, the function of B7-H4 was initially reported to be a negative regulator of T cell activation, proliferation and differentiation related to cytokine production and cytotoxic effector cell functions. B7-H4 is reportedly overexpressed in a variety tumors. B7-H4 expression by tumor macrophages appears to play a role in suppression antigen-specific T cell mediated immunity. Recent studies indicate that B7-H4 can also be a positive regulator of T cell responses. B7-H4 can be involved innate immunity as well, eg, by inhibiting neutrophil expansion.
The antibody was conjugated to BD Horizon™ BUV661 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 661-nm. BD Horizon Brilliant BUV661 can be excited by the ultraviolet laser (355 nm) and detected with a 670/25 filter and a 630 nm LP. Due to cross laser excitation of this dye, there may be significant spillover into channels detecting APC-like emissions (eg, 670/25-nm filter).
Due to spectral differences between labeled cells and beads, using BD™ CompBeads can result in incorrect spillover values when used with BD Horizon BUV661 reagents. Therefore, the use of BD CompBeads or BD CompBeads Plus to determine spillover values for these reagents is not recommended. Different BUV661 reagents (eg, CD4 vs. CD45) can have slightly different fluorescence spillover therefore, it may also be necessary to use clone-specific compensation controls when using these reagents.