Significant decline of peripheral myeloid dendritic cells following multiple trauma

Dendritic cells (DC) represent an important and integral part of the immune system and are potent initiators of inflammation. Two distinct subsets of DC have been identified: myeloid DC (MDC) and plasmacytoid DC (PDC), which differ widely in many respects. Despite the importance of the DC in the inflammatory response that occurs after severe multiple injury, there is a profound lack of information regarding the distribution and regulation of DC subtypes following multiple trauma. The main goal of this study was to assess whether the normal distribution of circulating DC subpopulations is altered during the first 5 d after multiple trauma.

Sixty-three patients with multiple trauma (ISS 31 +/- 15 points) and 11 healthy volunteers (control group) were enrolled. Blood samples were taken on admission (D0) and daily for the following 5 d. The percentages of MDC and PDC were determined by flow cytometry.

A significant decline of the MDC concentration was observable on days 3 to 5 after admission in comparison to the values obtained on the day of admission. The ratio of MDC to PDC decreased significantly (3-fold, P < 0.05). This reduction correlated significantly with changes observed in the plasma concentrations of IL-10 (r = 0.5; P < 0.05).

Our data demonstrate that multiple trauma is followed by a marked change in the subpopulation composition of the DC compartment, and that these changes are inversely associated with enhanced IL-10 plasma concentrations. This imbalance in the DC compartment favoring PDC concentrations may contribute to the immunological alterations that are observed following multiple trauma.