MULTIDIMENSIONAL FLOW-CYTOMETRIC ANALYSIS OF DENDRITIC CELLS IN PERIPHERAL-BLOOD OF NORMAL DONORS AND CANCER-PATIENTS

We studied the potential of multidimensional flow cytometry to evaluat e the frequency and maturation/activation status of dendritic cells in minimally manipulated peripheral blood mononuclear cell preparations (i.e., only separated on Ficoll-Hypaque) of normal donors and cancer p atients. A rare subset of HLA-DR+ leukocytes (less than 1% mononuclear cells) was detected in blood of normal donors that displayed all the features of dendritic cells: these cells had high forward-light-scatte r characteristics and coexpressed CD4, CD86 and CD54 surface antigens, but lacked the Lineage-associated surface markers of T cells, B cells , monocytes, granulocytes or NK i.e. they were CD3(-), CD19(-), CD20(- ), CD14(-), CD11b(-), CD16(-), CD56(-)). These physical and phenotypic properties were virtually identical to those of immunomagnetically so rted leukocytes characterized as dendritic-cells on the basis of morph ology, phenotype and high stimulatory activity in allogeneic mixed-lym phocyte cultures. Using this flow-cytometric approach we observed that the frequency of dendritic cell-like cells in peripheral blood mononu clear cell specimens of cancer patients receiving chemotherapy alone o r those recovering from stem cell transplantation was significantly lo wer than that of normal individuals (mean +/- SE: 0.36 +/- 0.05%, 0.14 +/- 0.06%, and 0.75 +/- 0.04% respectively). Multidimensional flow-cy tometric analysis of dendritic cells might represent an important new tool for assessing immunocompetence, and for monitoring the effects of therapeutic regimens on the immune system.