In early apoptosis, cells lose membrane phospholipid asymmetry, whilst the integrity of the cell membrane is maintained. The Annexin-V kits contain a viability dye to evaluate membrane integrity as well as annexin-V to assess membrane asymmetry.
In fact, phosphatidylserine (PS), a negatively charged phospholipid located in the inner surface of the plasma membrane, appears very early in apoptosis at the external cell surface. Annexin V, a calcium and phospholipid binding protein, binds preferentially to PS. The Annexin V kits employ recombinant annexin V labeled with biotin, fluorescein or R-phycoerythrin in together with the viability dyes propidium iodide (PI) or 7-amino actinomycin D (7-AAD).
Apoptotic cells are easily identified utilizing a rapid and simple staining procedure. Fixation of the cells is not necessary.
When cells are double-stained with annexin V and a viability dye, three different cell populations may be observed (see figure below): (i) live cells that do not stain either with annexin V or with the vital dye, (ii) necrotic or late apoptotic cells that stain with both annexin V and the vital dye, and (iii) early apoptotic cells that stain with annexin V only. Analysis may be performed on any flow cytometer equipped with a 488nm laser or Arc Lamp depending on the reagent kit chosen. Alternatively, the cells may be examined with a fluorescent microscope or cell imaging system equipped with the appropriate filters.
NOT ALL PRODUCTS ARE AVAILABLE IN ALL COUNTRIES
PRODUCT AVAILABILITY AND REGULATORY STATUS DEPENDS ON COUNTRY REGISTRATION PER APPLICABLE REGULATIONS
The listed regulatory status for products correspond to one of the below:
IVD: In Vitro Diagnostic Products. These products are labeled "For In Vitro Diagnostic Use."
ASR: Analyte Specific Reagents. These reagents are labeled "Analyte Specific Reagents. Analytical and performance characteristics are not established."
CE: Products intended for in vitro diagnostic use and conforming to European Directive (98/79/EC). (Note: Devices may be CE marked to other directives than (98/79/EC)
RUO: Research Use Only. These products are labeled "For Research Use Only. Not for use in diagnostic procedures."
LUO: Laboratory Use Only. These products are labeled "For Laboratory Use Only."
No Regulatory Status: Non-Medical Device or non-regulated articles. Not for use in diagnostic or therapeutic procedures.