Basically it is just what the name says. It is the mean of the fluorescence intensity in the fluorescence channel that you choose (FITC, PE, PerCP, etc.). It's value depends on the corresponding parameters you chose (you can change the intensity of each channel). It is useful if you have your cell population gated and let's say you stained with antibody CD38-PE. Then you choose the PE channel and check where the mean of the peak is. You know then if the cells are for example positive for CD38 if the mean fluorescence intensity of the sample exceeds the mean of the non stained control.

Carina already said what it is. I wanted to add that in FlowJo you actually have a function to define the MFI of a defined parameter in a defined gate. Select the gate you wish to analyze, and then klick on the "Add a statistics" button in the menu in the header of your workspace (it is a sigma symbol).
Upon klicking it, a window will pop up and you may now choose which function to use (e.g. arithmetic mean, geometric mean, median of fluorescent intensity etc...) and which fluorescent parameter to analyze.
Hope this helps.

Jan 20, 2012

Rohan Wales · Xi'an Jiaotong University Medical School

MFI refered to the fluorescence intensity of each event in average, represent the expression quantity of the the parameter you chosed on each event. In FACS,

## All Answers (4)

Carina Adamzyk· University Hospital RWTH AachenRyan Duggan· University of ChicagoLuka Cicin-Sain· Helmholtz Centre for Infection ResearchUpon klicking it, a window will pop up and you may now choose which function to use (e.g. arithmetic mean, geometric mean, median of fluorescent intensity etc...) and which fluorescent parameter to analyze.

Hope this helps.

Rohan Wales· Xi'an Jiaotong University Medical SchoolCan you help by adding an answer?