The 1F2 mAb reacts with Crry/p65, a cell-surface protein that blocks complement activation and C3 deposition by both the classical and alternative pathways. Based on nucleotide sequence identity, Crry/p65 is the genetic homologue of human CR1 (Complement Receptor 1). However, it has been proposed that Crry/p65 is the functional homologue of human MCP (Membrane Cofactor Protein) and/or DAF (Decay-Accelerating Factor), due to the similar functions these proteins share and the fact that Crry/p65 does not display CR1's complement-receptor activity. Crry/p65 is expressed in most organs, such as thymus, kidney, uterus, skin, lung, pancreas, heart, stomach, large and small intestine, and spleen. Platelets, brain, and muscle express low, but detectable levels of Crry/p65. In addition, Crry/p65 is expressed in J774 cells, bone marrow-derived macrophages, and thioglycollate-elicited peritoneal macrophages, as determined by RT-PCR. Crry is crucial in the regulation of complement activation during early mouse embryonic development and essential in fetomaternal tolerance. The 1F2 mAb partially blocks Crry/p65-mediated complement protection in vitro.
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.