Flow cytometer, a machine that utilizes the usage of light signals, has become one of the important machines or components in the studies of specific cell populations, cell surfaces, or even in detecting intracellular proteins. Due to its multiplex functionalities, while at the same time being very sensitive and specific, flow cytometer, or the technique of flow cytometry, has become a favourable and valuable tool for immunologists and clinicians for initial diagnosis of primary immunodeficiency diseases (PID), especially in studying cellular functional characteristics linked to PID. This paper will review key immunology tests of clinical flow cytometry, specifically in immunophenotyping, T cells classification and lymphocyte proliferation assays for their advantages and limitations in the field of PID. Importance of validation for the assays will be discussed. It is expected that development of validated immunology tests in clinical flow cytometry for PID diagnosis ensure standardized protocols, improve troubleshooting and disease interpretation, and improve the quality in patients’ diagnosis and management.
Flow cytometry