Quantitative identification of blood cell markers in human hematopoietic malignancies with diagnostic and prognostic significance.

Fluorescence intensity (FI) is the basis for classifying phenotypes by fluorescence-label flow cytometry. FI is of a relative value, but with calibration it can be expressed in stoichiometric units called molecules of equivalent soluble fluorochrome (MESF) that reflect the concentrations of the fluorescent conjugates and the receptors they stain. Flow cytometry allows in addition to the determination of positive cells, to establish even the intensity of fluorescent staining, that can be converted into antigen density. The concept of antigen density appears to improve the efficiency of immune techniques in the monitoring of hematopoietic malignancies. Quantitative immunophenotyping is thus suitable for the diagnosis of malignancy, contributes to prognosis and could provide new relevant pathophysiological informations. Quantitative analysis of some markers of leukemic cells could be a good model for the study of antigen modulation caused by chemotherapeutic agents. Standardized reagents and techniques for performing quantitative FI measurements on cytometers are just now emerging into practical use. This latter feature should see the expanding application in both, the basic science and medical applications, as the development of therapeutics increasingly targets specific cell receptors. FI data constitute a very important component of the analysis of cells in hematopoietic malignancy; standardized approach to instrument quality control, interlaboratory comparability of FI measurement and quality assurance is required.