The G-25.2 monoclonal antibody specifically recognizes CD11a which is also known as Leukocyte function-associated molecule 1 alpha chain (LFA-1A or LFA-1α). CD11a is a ~180 kDa type I transmembrane glycoprotein that is encoded by ITGAL (Integrin subunit alpha L) that belongs to integrin α-chain family. CD11a is a leucocyte adhesion receptor that noncovalently complexes with CD18 to form the LFA-1 heterodimer (CD11a/CD18) which binds to intercellular adhesion molecules (ICAMs) expressed on target tissues including ICAM-1 (CD54), ICAM-2 (CD102), ICAM-3 (CD50), ICAM-4, or ICAM-5. The CD11a antigen is expressed on virtually all normal peripheral blood leucocytes. It is essential for many immune responses that require cell-to-cell contact, such as lymphocyte adhesion, natural killer (NK) and T-lymphocyte cytolysis, and T lymphocyte proliferation. Activation of lymphocytes through the T-cell antigen receptor (TCR) upregulates LFA-1 function, converting the antigen to a high-avidity state. Expression of LFA-1 on monocytes is upregulated by γ-interferon (IFN-γ). While normal cells possess both the α and β LFA-1 chains, cells of subjects with some leukemias, lymphomas, or leucocyte adhesion deficiency (LAD) may lack the entire LFA-1 molecule or the α or β chain. The absence of LFA-1 on tumor cells may provide a mechanism for their escape from immune surveillance.
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.