Monitoring human blood dendritic cell numbers in normal individuals and instem cell transplantation

Dendritic cells (DC) originate from a bone marrow (BM) precursor and circul ate via the blood to most: body tissues where they fulfill a role in antige n surveillance. Little is known about DC numbers in disease, although the r eported increase in tissue DC turnover due to inflammatory stimuli suggests that blood DC numbers may be altered in some clinical situations. The lack of a defined method for counting De has limited patient studies. We theref ore developed a method suitable for routine monitoring of blood DC numbers, using the CMRF44 monoclonal antibody (MoAb) and flow cytometry to identify DC. A normal range was determined from samples drawn from 103 healthy adul ts. The mean percentage of DC present in blood mononuclear cells (MNC) was 0.42%, and the mean absolute DG count was 10 x 10(6) DC/L blood. The normal ranges for DC (mean +/- 1.96 standard deviation [SD]) were 0.15% to 0.70% MNC or 3 to 17 x 106 DC/L blood. This method has applications for monitorin g attempts to mobilize DC into the blood to facilitate their collection for immunotherapeutic purposes and for counting blood DC in other patients. In preliminary studies, we have found a statistically significant decrease in the blood DC counts in individuals at the time of blood stem cell harvest and in patients with acute illnesses, including allogeneic bone marrow tran splant (BMT) recipients with acute graft-versus-host disease (aGVHD). (C) 1 999 by The American Society of Hematology.