Flow Cytometry

By Malcolm Weir, DVM, MSc, MPH; Kristiina Ruotsalo, DVM, DVSc, Dip ACVP & Margo S. Tant, BSc, DVM, DVSc

What is flow cytometry?

Flow cytometry is a laboratory technique that can be used for counting, examining, and sorting cells. The technology to perform flow cytometry is often incorporated into automated laboratory equipment such as hematology (blood) analyzers.

Using flow cytometry, the sample is passed through a light source, typically a laser. As the cells in the sample move through the path of the light source, they will scatter the light. The pattern of scattering is a function of both the size of the cell and its internal complexity. The scattered light is captured by lenses, and translated into an electrical signal, which is further analyzed by a computer program and displayed as a graphical representation of the cell populations within the sample.

What types of samples can be analyzed by flow cytometry?

Essentially anything that can be suspended within a liquid (thereby allowing a smooth flow of material through the flow chamber) can be analyzed. Within veterinary medicine, the most common samples analyzed are peripheral blood samples (blood that travels through the heart, arteries, veins and capillaries), and cells derived from tissues (lymph nodes, bone marrow) or body cavity fluids.


What are the uses of flow cytometry in veterinary medicine?

As mentioned, flow cytometry is incorporated into automated hematology analyzers for the counting and grouping of cells within a blood sample.

"Another use for flow cytometry is the characterization of cellular subpopulations."

Another use for flow cytometry is the characterization of cellular subpopulations. For example, it may be difficult on occasion to distinguish benign from malignant (cancerous) lymphocytes (a type of white blood cell) within a blood or tissue sample based on microscopic cellular features alone. Using flow cytometry and antibodies to specific proteins on the lymphocyte cell membrane, the lymphocytes present within a sample can be broken down into subpopulations. The presence of many different subpopulations of lymphocytes would be more consistent with a benign inflammatory or reactive process, whereas the presence of a uniform population would be supportive of a malignant lymphocyte population.

Can flow cytometry be done in general veterinary practice?

No. Typically, the equipment needed to perform this technique and the technical expertise required to interpret the findings are only available in university or referral settings. However, many such centers do accept samples from veterinary clinics for analysis.

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