Cahill LA, Guo F, Nguyen J, et al. - Using time-of-flight mass cytometry, researchers desired to know how trauma plasma influences normal peripheral blood mononuclear cell (PBMC) activation to gain insights into the kinetics and nature of trauma-induced circulating factors on human immune cell populations. PBMCs from healthy participants were cultured with 5% plasma (healthy, trauma-1day, or trauma-3day) or known damage associated molecular patterns (DAMPs) for 24 hours. They proposed that circulating factors in trauma plasma will cause phenotypic activation of normal human immune cell subsets. Specific changes in immune cell subsets that respond to trauma plasma were identified using an unbiased approach. Furthermore, CD11c+ NK cells expanded in response to DAMPs and LPS, indicating that similar components in trauma plasma might also be responding. Collectively, the data show that the normal response of PBMC to trauma plasma includes marked changes in specific subsets of NK and CD8+ T cell populations.