Surgical and physical stress increases circulating blood dendritic cell counts independently of monocyte counts

Dendritic cells (DCs) are specialized antigen-presenting cells that have th e unique ability to initiate a primary immune response. The effect of physi ologic stress on circulating blood DCs has thus far not been studied. In th is study, we applied a recently developed method of counting blood DCs to t est the hypothesis that significant stress to the body such as surgery and exercise might induce measurable changes in the DC numbers, subsets, phenot ype, and function. Twenty-six patients scheduled for elective laparoscopic cholecystectomy, 4 for elective hysterectomy,56 controls, and 5 volunteers who underwent a stress exercise test were enrolled in the study. Absolute D C counts increased acutely (71.7% +/- 11% [SEM], p = .0001) in response to the stress of surgery and dropped below preoperative levels (-25% +/- 14% [ SEM], P = .05) on days 2-3, The perioperative DC subset balance remained co nstant. Interestingly, DC counts changed independently of monocyte counts. Exercise also induced a rise in DC counts but coincidentally with monocyte counts. Surprisingly, no phenotypic or functional activation of DCs was see n in either stress situations in vivo. DCs are rapidly mobilized into the c irculation in response to surgical and exercise stress, which may serve to prepare the host's immune defenses against trauma. The independent regulati on of the DC and monocyte counts reinforces the distinction between these 2 cell populations. (C) 2001 by The American Society of Hematology.