The WDF channel uses specific lysis and staining reagents to distinguish different blood cells. The lysing reagent hemolyses erythrocytes and increases the membrane permeability of leukocytes, revealing morphological differences. Fluorescent dyes bind to nucleic acids and intracellular organelles, resulting in differences in fluorescence signal between cell types. Based on fluorescence and light scattering, a scattergram is generated, after which an analysis algorithm identifies the different blood cell types.

In the WDF channel, lymphocytes , monocytes , neutrophilic granulocytes and eosinophils are distinguished. Basophilic granulocytes can also be seen but are quantified in the WNR channel.

Eosinophilic granulocytes have a relatively high SSC because the reagent affects eosinophilic granulation.