Incorrect Use of Isotype Controls for Gating Dim Markers

Symptom

Gates set using isotype controls for dim or activation markers result in inaccurate population identification, with either false negatives (missed positive cells) or false positives.

1. 1 Isotype controls measure only non-specific binding, not fluorescence spillover from other channels
2. 2 Dim activation markers (CD25, CD69, HLA-DR) have subtle signal differences that isotypes cannot accurately define
3. 3 Multicolor panels with spectral overlap require spillover-corrected gating strategies
4. 4 Isotype controls do not account for biological variability in low-expressing populations

1. 1 Use FMO (Fluorescence Minus One) controls for all dim markers, activation markers, and multicolor panels to accurately define gating boundaries
2. 2 For spectral cytometry systems, always rely on FMO controls rather than isotype controls
3. 3 Reserve isotype controls for assessing overall background in high-background samples (myeloid cells, tumor cells), not for gating
4. 4 Establish gates using biological controls (unstimulated vs stimulated cells) when available
5. 5 Perform proper compensation and use single-stained controls to address spillover issues

Related Video (2)

BD Biosciences ★ 85

Choosing Proper Flow Cytometry Controls

"Directly addresses selecting appropriate flow cytometry controls, including isotype controls and their proper use in experimental design"

BD Biosciences ★ 78

Flow Cytometry Compensation Tips and Tricks

"Covers compensation strategies which are closely related to understanding spillover artifacts that isotype controls alone cannot address"