Flow cytometry is a powerful tool for analyzing cellular characteristics, including cell size and granularity, which are essential for identifying different cell populations. These parameters are typically measured using forward scatter (FSC) and side scatter (SSC) signals.
Forward Scatter (FSC) - Cell Size
FSC measures the light scattered along the path of the laser, primarily reflecting cell size. Larger cells scatter more light, resulting in higher FSC signals.
Side Scatter (SSC) - Granularity/Internal Complexity
SSC measures the light scattered at 90 degrees to the laser, indicating granularity and internal complexity. Cells with more granules, organelles, or nuclear complexity (such as neutrophils and eosinophils) exhibit higher SSC values.
FSC vs. SSC Plots for Cell Population Differentiation
The FSC versus SSC scatter plot aids in classifying cells based on size and granularity:
Lymphocytes: Low FSC, low SSC.
Monocytes: Intermediate FSC, intermediate SSC.
Granulocytes (neutrophils, eosinophils, basophils): High FSC and high SSC.
Dead/Residual Cells: Very low FSC and SSC.
Profiling immune cells (e.g., lymphocytes, monocytes, granulocytes).
Detection of apoptosis (shrunken cells exhibit reduced FSC).
Identification of stem cells and blast cells (low granularity, intermediate size).
Analysis of bacteria and particles (differentiation based on size).