Molecular/HIV laboratory

Flow cytometry - HIV

Summary

Science

Clinical

Science

Individual populations of immune cells, with specific roles in infection control, have different groups of molecules on their surface, this characteristic is useful for quantifying the cellular populations. As with many other techniques used in the immunology laboratory, 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 connected to dyes (fluorochromes) that emit light at specific wavelengths when excited by light at a lower wavelength (curriculum), several different colours attached to antibodies with different specificities can be used in the same sample to identify different cell classes. Cells labelled with the different antibodies are passed rapidly in single file through a laser beam that excites the dye molecules. The light that is emitted at different at different wavelengths is detected through a series of finely aligned detectors. In addition the shadow of the body of the cell passing through the laser beam is recorded and these measurement are extrapolated to determine how big and granular they are. 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. CD4 T cells are the most significant cellular indicators of disease progression in HIV so a scientist can differentiate and quantify them based on their medium size (relative to other blood cells) low granularity and strong binding with light fluorochrome labelled antibodies targeted against the CD4 cell surface marker.

• Background
• Clinical