High Background in Biological Control Sample (Flow Cytometry (Controls))

Question

Accepted Answer

Biological control (e.g., unstimulated sample in stimulation assay) shows unexpectedly high background, making it difficult to set clear positive/negative boundaries. Common causes: 1) Unstimulated sample shows elevated baseline expression of the marker being studied 2) Cells in biological control sample were inadvertently activated during handling or preparation 3) High autofluorescence or endogenous marker expression in the control cell population 4) Contamination or carryover from experimental samples into control sample Solutions: 1) Carefully handle biological control samples to avoid inadvertent cell activation during preparation 2) Verify that control samples are truly representative of negative expression state 3) Consider using FMO or isotype controls in addition to biological controls when high background is observed 4) Optimize cell preparation protocols to minimize autofluorescence and maintain cells in unstimulated state 5) Use freshly prepared biological controls and process them identically to experimental samples except for the variable being tested