FACS data analysis

Once light signals are converted to electronic pulses and then to numbers, the data must be stored by the computer system. Once the file is saved, there are many different ways to display the results. This analysis is also necessary to perform the gating step, in order to sort and collect the target cells.

A single parameter can be displayed as a single univariate histogram (Figure 1), where the x-axis represents the parameter’s signal value and the y-axis represents the number of events, which is the same as the number of cells. Higher/brighter signals have higher values in the x-axis and therefore will be displayed on the right side x-axis, while lower/darker signals will be located on the left side of the x-axis.

Figure 1. Univariate histogram displaying one parameter: fluorescence.

Two parameters can also be displayed simultaneously in a plot. One parameter is displayed on the x-axis and the other parameter is displayed on the y-axis. This is really helpful when a heterogeneous population of cells needs to be sorted to differentiate cell types, for instance using FSC and SSC values at the same time.