The flow cytometry test performed yesterday got me curious as to the difference between the staining of dead cells. An important concept in our lab is the distinction between programmed cell death and naturally occurring neuronal cell death. Apoptosis is programming of cell extravasation due to damages of the cell to the extent that it is no longer viable.
To prevent inflammation and the spread to other nearby cells, Annexin A-1 is responsible for antiinflammatory response. Annexin-A1 reduces inflammation of tissues by binding to its receptor on leukocytes. Annexin-A1 signalling allows for a more elegant removal of the damaged or infected cell rather than letting leukocytes extravasation from creating a worse inflammatory response.
Annexin-A1 also promotes apoptotic mechanism by marking cells for removal. It can also be used as a cell surface protein to mark tumors to be targeted in immunotherapies with antibodies againist Annexin A1. Glucocorticoids used for the supression of inflammation utilizes annexin to suppress phospholipase A2 from cleaving fatty acids to release arachidonic acid involved in mediation of the inflammatory response. In this particular experiment, FITC was used as the marker tag.
Propidium Iodide Staining. PI is a compound that penetrates the cellular membrane and intercalates between the double-stranded nucleic acids of dead and dying cells.
https://cyto.mednet.ucla.edu/Protocols/pi.htm