Flow cytometry relies on detecting membrane molecules by using what type of label on antibodies?

• A. Fluorescent-labeled antibody
• B. Enzyme-labeled antibody
• C. Radioactive-labeled antibody
• D. Complement-coated antibodies

Answer: (A)

Flow cytometry detects membrane molecules by tagging antibodies with fluorescent dyes. When these fluorescently labeled antibodies bind to specific surface proteins, the fluorophores are excited by a laser as cells flow past the detectors. The emitted light from each fluorophore is measured, allowing identification and quantification of the target molecules on individual cells. Using multiple fluorescent labels lets you analyze several membrane proteins at once by separating signals across different emission wavelengths. Other label types aren’t suited to flow cytometry: enzyme labels require substrate reactions and are better for bulk measurements, radioactive labels pose safety and detector-compatibility issues, and complement-coated antibodies don’t provide the direct fluorescent signal needed for single-cell detection.