What is flow cytometry used for in an immunology laboratory?

• A. It sequences T-cell receptors.
• B. It measures blood pressure in vessels.
• C. It cultures cells and measures growth rate.
• D. It analyzes cell properties (size, granularity, surface markers) with fluorescent antibodies to phenotype cells.

Answer: (D)

Flow cytometry analyzes physical and chemical properties of individual cells as they flow past lasers. It uses forward scatter to estimate cell size and side scatter for internal complexity (granularity). By staining cells with fluorescent antibodies against specific surface (and sometimes intracellular) markers, you can quickly identify and quantify different cell populations and phenotypes. This multiplex capability lets you determine which cells are present, in what proportions, and with what activation or differentiation markers, all in one assay.

The other activities aren’t what flow cytometry does: sequencing T-cell receptors is a genomic method, measuring blood pressure is a physiological measurement, and culturing cells with growth-rate assessment is cell culture.