Flow cytometry: basic concepts and clinical applications in immunodiagnostics.

OBJECTIVE: To review current and possible future clinical applications of flow cytometry in immunodiagnostic procedures. DATA SOURCES: Recent research and review articles and textbooks on laboratory diagnosis and flow cytometry. STUDY SELECTION: Not applicable. DATA EXTRACTION: Performed by the author. DATA SYNTHESIS: Flow cytometry is the measurement of cellular and fluorescent properties of stained cells in a fluid stream as they move past a set of fixed detectors. The instruments are capable of measuring these properties on thousands of cells in but a few seconds. Many specimen types can be analyzed on the flow cytometer. CONCLUSION: Flow cytometry is especially useful in monitoring immunodeficiencies, leukemias, and other malignancies, but it has other uses, as well. Improvements in instruments, reagents, and methods will cause an increase in the number of applications for flow cytometry. More laboratories will be able to purchase the equipment as it becomes less expensive. Flow cytometry provides the clinician valuable information in the diagnosis and treatment of disease.

A patient with simultaneous absence of "classical" natural killer cells (CD3-, CD16+, and NKH1+) and expansion of CD3+, CD4-, CD8-, NKH1+ subset.

The clinical manifestations of putative natural killer (NK) cell deficiency are not well-known but theoretically should include recurrent tumors and systemic viral infections. In this article, we discuss a patient with recurrent condylomata, vulvar and cervical carcinoma in situ, pulmonary infiltrates of unknown significance, and a hypercoagulable state. This patient has a dramatic persistent deficiency in her circulating "classic" NK cells (CD3-, CD16+, NKH1+) and a simultaneous persistent expansion of a normally minor lymphocyte cell subset (CD3+, CD4-, CD8-, NKH1+) that does not express the alpha beta heterodimer of the T cell receptor. T-lymphocyte function, as measured by mitogen and alloantigen responsiveness in vitro, was normal. The coexistence of this particular clinical complex with this unusual set of laboratory abnormalities tends to emphasize our meager understanding of the biologic role of NK cells. At the very least, these findings suggest that the clinical manifestations of NK cell deficiency need not be dominated by disseminated systemic viral infections and that perhaps there should be a higher index of suspicion for the scrutinization of NK cell function.