Cellular Laboratory

Flow cytometry in Primary Immunodeficiency and Leukemia

Summary

Science

Clinical

Science

Individual populations of immune system cells with specific roles and at different stages of maturation have different groups of molecules on their surface. This characteristic is useful for quantifying the different populations as we can identify them based on these specific markers. Commercially available antibodies that have specificity for single unique surface molecules are mixed with the patient’s blood so that they can bind to their targets. These antibody labels are joined to dyes (fluorochromes) that emit light at specific wavelengths when excited by light at a lower wavelength, several different colours attached to antibodies with different specificities can be used in the same sample. Cells tagged with the different antibodies are rapidly passed in single file through a laser beam that excites the dye molecules. The light that is emitted at different wavelengths is detected through a series of finely aligned detectors. In addition the cell itself casts a unique shadow as it passes through the laser beam. This is recorded and these measurements are extrapolated to determine the size and granularity of the cell. The results are represented graphically and by using this data every cell is recorded as having a specific signature based on size, granularity, and abundance of surface markers.

In some primary immunodeficiencies, certain populations of cells are absent or may have crucial receptor molecules missing on their surfaces. Flow cytometry can be used to check if these populations are present and if they have their full complement of receptor and activation molecules. Leukemia is typified by an abundance of single type of cell at one specific stage of development undergoing rapid proliferation this means that it will be the major type of cell in the sample and in turn results in a reduction of all other cells. Using flow cytometry, this population can be determined as a homogeneous group of cells with a discrete set of surface marker characteristics specific for the type of leukemia.

• Background
• Clinical