Although Streptococcus pneumoniae is usually found as a commensal in healthy individuals, it can act as a pathogen in trauma patients, causing such complications as early-onset pneumonia and sepsis. We discovered that treating mice with an A-class CpG-oligodeoxynucleotide (ODN) at 2 h after traumatic injury significantly improved mouse survival following early-onset secondary lung infection with S. pneumoniae. This study used mass cytometry (cytometry by time-of-flight) and Luminex technologies to characterize the cellular immune response to secondary S. pneumoniae lung infection at 1 and 3 d postinfection. We found increased expression of CD14, CD64, and PD-L1 on F4-80+ and F4-80+CD11c+ macrophages, CD11c+ dendritic cells, and CD14+CD172a+ cells after burn-injury and infection, supporting previous reports of innate immune cell activation in sepsis. CpG-ODN treatment at 2 h after burn-injury reversed these effects; improved pathogen clearance; and led to an increased expression of CD25, CD27, MHCII, and IL-17 on or in TCRγδ cells at 1 d postinfection. At 3 d postinfection, CpG-ODN treatment increased the expression of PD-L1 on innate cell subsets. Furthermore, we analyzed cytokine levels in lung-washout samples of TCRγδ cell–depleted (TCRγδ−) mice to demonstrate that the effects of CpG-ODN on cytokine expression after burn-injury and S. pneumoniae infection rely on functional TCRγδ cells. In summary, we demonstrate that cytometry by time-of-flight provides an effective strategy to systematically identify specific cellular phenotypic responses to trauma and bacterial pneumonia and to discover changes in immune system phenotypes associated with beneficial immunotherapy.
This article is featured in In This Issue, p.519
This work was supported by National Institutes of Health Grants AI092905-04 and AI107360-02, Deutsche Forschungsgemeinschaft Grant WA 3426/1-1, the Brigham and Women’s Hospital Biomedical Research Institute, and the Harvard Medical Area CyTOF Consortium.
Abbreviations used in this article:
- cytometry by time-of-flight
- dendritic cell
- regulatory T cell
- visualization algorithm for stochastic neighbor embedding
- Received March 11, 2015.
- Accepted November 9, 2015.
- Copyright © 2016 by The American Association of Immunologists, Inc.