Artifactual phosphorylation signals from pre-fixation surface staining

Symptom

Phospho-flow cytometry results show altered phosphorylation patterns when surface antibodies are added before fixation. Antibody binding to surface antigens triggers intracellular signaling cascades that confound true phosphorylation measurements.

1. 1 Surface antibody-antigen binding activates receptor-mediated signaling pathways within seconds to minutes
2. 2 Crosslinking of surface receptors by antibodies induces artificial phosphorylation events
3. 3 Time delay between antibody addition and fixation allows signal transduction artifact accumulation
4. 4 Fc receptor engagement by antibody constant regions triggers non-specific kinase activation

1. 1 Fix cells BEFORE adding any surface antibodies when analyzing phosphorylation targets
2. 2 Follow BioLegend True-Phos Perm Buffer protocol with fixation preceding all antibody staining steps
3. 3 Minimize time between sample harvest and fixation to <5 minutes for phospho-epitope preservation
4. 4 Use ice-cold buffers and maintain samples at 4°C to slow enzymatic activity before fixation
5. 5 Stain surface markers after permeabilization on fixed cells to avoid signaling artifacts

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