Circulating blood dendritic cells from myeloid leukemia patients display quantitative and cytogenetic abnormalities as well as functional impairment

Dendritic cells (DCs) are responsible for the initiation of immune response s. Two distinct subsets of blood DCs have been characterized thus far. Myel oid DCs (MDCs) and plasmacytoid monocytes (PDCs) were shown to be able to p romote polarization of naive T cells. This study shows a dramatic quantitat ive imbalance in both circulating blood DC subsets in 37 patients with acut e myeloid leukemias. Eleven patients (30%) displayed a normal quantitative profile (MDC mean, 0.37% +/- 0.21%; range, 0.01% to 0.78%; PDC mean, 0.21% +/- 0.24%; range, 0.04% to 0.62%), whereas 22 (59%) showed a tremendous exp ansion of MDCs (9 patients: mean, 16.76% +/- 14.03%; range, 1.36% to 41%), PDCs (4 patients: mean, 7.28% +/- 6.84%; range, 1% to 14%), or both subsets (9 patients: MDC mean, 10.86% +/- 12.36%; range, 1.02% to 37.1%; PDC mean, 4.25% +/- 3.78%; range, 1.14% to 13.04%). Finally, in 4 patients (11%), no DC subsets were detectable. Both MDC and PDC subsets exhibited the origina l leukemic chromosomal abnormality. Ex vivo, leukemic PDCs, but not leukemi c MDCs, had Impaired capacity for maturation and decreased allostimulatory, activity. Also, leukemic PDCs were altered in their ability to secrete int erferon-alpha. These data provide evidence that DC subsets in vivo may be a ffected by leukemogenesis and may contribute to leukemia escape from Immune control. (C) 2001 by The American Society of Hematology.