Inconsistent Results Between Wells (Edge Effects)

Symptom

Results vary significantly between wells that should be replicates. Edge wells often show different spot counts or characteristics compared to central wells, creating systematic position-dependent effects.

1. 1 Plates stacked during cell incubation causing non-uniform temperature distribution
2. 2 Cell suspension not well-mixed when adding to wells resulting in uneven cell numbers
3. 3 Membrane not pretreated uniformly across all wells
4. 4 Inadequate washing after ethanol treatment affecting different wells variably

1. 1 Never stack plates during cell incubation to ensure uniform temperature across all wells
2. 2 Prepare well-mixed single-cell suspension; gently mix before each aliquot addition
3. 3 Ensure uniform ethanol pretreatment of entire membrane surface
4. 4 Wash membrane thoroughly with PBS 3× after ethanol treatment to ensure uniform removal

Related Video (2)

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ELISpot tutorial: step-by-step full assay protocol

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