In flow cytometry, what does forward scatter measure?

In flow cytometry, forward scatter primarily measures the size of cells. When particles, such as cells, pass through a laser beam within the flow cytometer, the light that is scattered forward correlates with the size of the cells. Larger cells will scatter more light in the forward direction compared to smaller cells, allowing operators to obtain a relative estimation of cell size.

On the other hand, granularity, cell viability, and cell surface proteins involve different measurements. Granularity refers to the complexity or internal structures of the cells, which is typically assessed using side scatter, not forward scatter. Cell viability is usually measured through fluorescent dyes that indicate living versus dead cells, and cell surface proteins are analyzed by staining with specific antibodies followed by detection methods that do not rely solely on forward scatter measurements.