Mazzeo AT et al. (2006) Severe human traumatic brain injury, but not cyclosporin A treatment, depresses activated T lymphocytes early after injury. J Neurotrauma 23: 962–975

Severe traumatic brain injury (TBI) can lead to immune system impairment, resulting in increased morbidity and mortality. Mazzeo et al. have studied the early effect of severe TBI on cell-mediated immunity and examined whether early infusion of the immunosuppressant ciclosporin A—which has been shown to be beneficial in TBI—further affects early cell-mediated immunological function after TBI.

The study included 49 patients with severe TBI and a Glasgow Coma Scale score of ≤8. Thirty-six patients received one or two 24 h infusions of ciclosporin, and 10 patients received placebo; 3 patients were not included in the ciclosporin substudy.

At admission, CD3+, CD4+ and CD8+ T-lymphocyte counts were low in 65%, 70% and 39% of patients, respectively. Injury severity score increased with decreasing T-lymphocyte counts, indicating that patients with the most-severe injuries had the worst immunological impairment. Reduced T-lymphocyte counts were also associated with increased susceptibility to pulmonary infection. Higher injury severity scores were associated with worse neurological outcomes. Absolute T-lymphocyte counts were similar in patients receiving ciclosporin and patients receiving placebo. Histopathological investigation of contused brain tissue from one patient showed large numbers of T cells—mainly CD8+ T cells—infiltrating the traumatized brain parenchyma.

The authors conclude that cellular immunosuppression often follows TBI, and that a reduction in T-lymphocyte count is related to worse neurological outcome and increased risk of pulmonary infection. They state that ciclosporin administration after head injury is safe and does not interfere with the cellular immune response.