Fluorescence intensity of immunostained cells as a diagnostic aid in lymphoid leukemias

The standardized fluorescence intensity (FI) of immunostained normal and malignant B-cells was measured as a method of evaluating cellular heterogeneity between lymphoid malignancies. Mature B-cells from peripheral blood lymphocytes (PBL) of different individuals demonstrated characteristic peaks of FI when specific monoclonal antibodies (MoAbs) were employed in standard flow cytometric procedures. Malignant cells from patients with lymphoid leukemias demonstrated FI that differed from that of normal B-cells with various MoAbs and that differed among categories of leukemia. By using a panel of MoAbs reactive with B-cells, as well as a T200 (CD45) antigen, a scheme of malignant cell differentiation may be produced that approximates stages of normal B-cell differentiation. When the FI of malignant cells differs from that of normal cells, or when atypical peaks (or additional peaks) of FI are present in flow cytometric histograms, the investigator should be alerted to the probability of abnormal cell populations. In addition, it is frequently possible to use this information to help classify malignancies, thereby contributing to identification of small numbers of malignant B-cells in otherwise equivocal situations.