Dynamic changes in trauma-induced myeloid-derived suppressor cells after polytrauma are associated with an increased...

There is a strong association between severity of injury and an increased susceptibility to infection after injury. T cell dysfunctions are central to the development of infections following a trauma. Trauma-induced myeloid-derived suppressor cells (MDSCs) can suppress T cell functions, and the process is associated with poor clinical outcome. In this study, we compared the dynamic changes in trauma-induced MDSCs in two trauma animal models.

Rats were divided into three groups as follows: the control group, the femur fracture (FFx) group, and the polytrauma (PT) group. Animals were sacrificed at 2, 6, 12, 18, or 24 h postoperatively, and spleen was harvested for study. The MDSCs were identified by a flow cytometry and calculated. Incorporation of [³H]thymidine was used to measure T cell proliferation. The results showed that the number of MDSCs in the spleen reached a peak 2 h after the trauma in both the groups. The peak number of MDSCs in the PT group was about four times greater (P<0.001); and in the FFx group, about one and a half times more (P=0.003) than in the control group. The increased level of MDSCs returned to normal after 18 h in the PT group, and after 6 h in the FFx group, post-surgery. Incorporation of [³H]thymidine showed that MDSCs induced by trauma suppressed T cell proliferation.

These results suggest that polytrauma stress represent a more extensive MDSCs expansion which may contribute to an increased susceptibility to infection.