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CD8+ TEMRA cells: higher background levels may predict delayed fracture healing
DOI:10.1038/bonekey.2013.103
Between 5 and 15% of fracture patients experience delayed healing. Reinke et al. investigated how bone fracture repair can be affected by the immune status of an individual.
The group studied 15 patients with a closed tibia head fracture, monitoring their rate and extent of fracture healing and then characterizing the function and activity of their immune system. They found no differences between patients with normal healing and delayed healing with respect to levels of interleukin-6 or -8, tumor necrosis factor-α or interferon-γ. Further analysis of the peripheral blood showed that patients showing delayed healing had >70% more CD8+CD11a++ T cells compared to patients with normal healing and compared to healthy controls.
A higher level of a subset of these T cells, termed CD8+ TEMRA, which show enhanced expression of CD57 but lack CD28, was directly correlated with delayed fracture healing. Levels of these cells were not elevated because of the recent fracture trauma but rather they appeared to be part of the individual’s stable immune profile.
Experiments in a mouse osteotomy model showed that transferring CD8+ TEMRA cells delayed fracture healing, but depleting this cell type led to faster regeneration and healing due to endogenous mechanisms.
Editor’s comment: This study provides further evidence that the immune system can regulate fracture healing. CD8+ TEMRA cells may be a useful marker for predicting fracture healing and may help to target at-risk patients with suitable therapeutic interventions.
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