Functional diagnostics in flow cytometry: An innovative cellular approach for clinical immunology and metabolism
Flow cytometry is now a key technology in clinical diagnostics. It enables the rapid analysis of thousands of individual cells and provides precise data on their physical, biochemical, and functional properties. This technique is increasingly being used to develop functional diagnostics, particularly in clinical immunology and metabolic diseases.
What is functional diagnostics?
Unlike conventional tests that measure the amount of a biomarker (such as a protein or antibody), functional diagnostics captures the actual biological activity of cells. This allows us to understand how cells respond to a stimulus or perform a function. This is particularly useful for the detection of immune, allergic, or metabolic diseases.
The Role of Flow Cytometry
Flow cytometry is a laboratory method that analyzes cells suspended in a fluid as they pass through a laser beam. Cells are labeled with fluorescent markers that bind to specific surface proteins, intracellular components, or metabolic products. The machine then measures:
- Cell size and granularity
- Presence or absence of specific markers
- Cellular responses to external stimuli
- Production of reactive molecules
Key Functional Flow Cytometry-Based Diagnostics
Basophil Activation Test (BAT) – Allergy Testing
This test evaluates the allergen-induced activation of basophils, a type of white blood cell involved in allergic reactions. After exposure to specific allergens, the test detects markers like CD63 or CD203c to assess the degranulation of basophils.
Neutrophil Chemotaxis Assay
This test measures the ability of neutrophils to migrate toward chemical signals (chemoattractants) that simulate inflammation. Reduced chemotaxis can indicate immune system defects and susceptibility to infections.
Leukocyte Oxidative Burst Test
This assay measures the production of reactive oxygen species (ROS) by neutrophils or monocytes upon stimulation. It’s particularly used to detect chronic granulomatous disease (CGD) or other oxidative dysfunctions. A reduced oxidative burst means impaired microbial killing.
Phagocytosis Assay
This test evaluates the ability of leukocytes to engulf pathogens or particles, an essential immune function. Cells are incubated with fluorescently labeled bacteria or particles, and uptake is measured by flow cytometry.
Natural Killer (NK) Cell Cytotoxicity Assay
NK cells are vital for immune surveillance against tumors and viruses. This test measures their ability to kill target cells, providing key information in cases of immunodeficiency or during immunotherapy monitoring.
LDL Receptor Expression on Monocytes
This assay evaluates the number of LDL receptors (LDL-R) on monocytes, helping to understand disorders of lipid metabolism such as familial hypercholesterolemia. It may also assist in cardiovascular risk assessment.