Patient Test Information

Immunophenotyping

Originally, glass slides with fixed tissue sections were treated with an antibody that was specific for a type of antigen typically found on certain abnormal cells associated with a particular leukemia or lymphoma. These antibodies were often linked with a fluorescence or a peroxidase indicator that would make these abnormal cells visible when observed under a microscope. Immunohistochemistry is based upon immunologic cellular properties and has proven to be particularly valuable in evaluating tissue samples that help in establishing a diagnosis or identifying relapse.

Another technique is flow cytometry and is performed by processing a blood, bone marrow, tissue, or fluid sample by adding specific antibodies that have been tagged with fluorescent markers. These antibodies will bind to corresponding antigens on the white blood cells (WBCs), if present, and are often referred to as cell markers. The WBCs are suspended in a physiologic solution and passed through a flow cytometer. The cell suspension is forced through a fluid stream that passes multiple laser beams causing deflection or absorption of the laser light. These light changes are identified by very sensitive detectors that analyze individual cells based on various physical properties.

The flow cytometer rapidly measures characteristics about each cell, such as its size and granularity (internal cellular structures), and evaluates the type and quantity of fluorescent antigen-antibody complexes that are present. The advantage of flow cytometry over Immunohistochemistry is that thousands of cells are evaluated during the test. Based on the physical characteristics of the abnormal cells and the presence (or absence) of fluorescence, the investigator can quickly determine the type of leukemia or lymphoma that may be present.