Surface Epitope Masked After Fixation (Flow Cytometry (Sample Considerations))

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Accepted Answer

Surface marker staining fails or weakens when performed after cell fixation. Some antibody clones lose binding capacity to fixed cells. Common causes: 1) Paraformaldehyde fixation induces protein crosslinking that masks epitopes 2) Conformational epitopes are disrupted by fixative-induced structural changes 3) Specific antibody clones are not compatible with post-fixation surface staining 4) Fixation protocol (concentration, time, temperature) not optimized for target epitope preservation Solutions: 1) Perform surface staining before cell fixation as the default workflow 2) Consult BioLegend Fixation page to identify antibody clones compatible with post-fixation surface staining 3) Contact BioLegend technical support (tech@biolegend.com) if clone compatibility information is unavailable 4) Test alternative antibody clones targeting the same marker for fixation tolerance 5) Optimize fixation conditions (e.g., 1-4% paraformaldehyde, 10-20 minutes, 4°C or room temperature) for each critical marker 6) Use fixation-compatible fluorophores and avoid tandem dyes prone to dissociation