Cell viability
The cell viability of a sample is determined using the total cell count and the count of non-viable cells (see the figure below).
When a sample is mixed with Reagent A100 and Reagent B a lysis of the viable cell membrane takes place rendering all the cell nuclei susceptible to staining with propidium iodide (PI) resulting in a total cell count.
Non-viable cells however are permeable without treatment and are therefore stained directly with PI, resulting in a non-viable cell count.