Differential fracture response to traumatic brain injury suggests dominance of neuroinflammatory response in polytrauma.

Polytraumatic injuries, specifically long bone fracture and traumatic brain injury (TBI), frequently occur together. Clinical observation has long held that TBI can accelerate fracture healing, yet the complexity and heterogeneity of these injuries has produced conflicting data with limited information on underlying mechanisms. We developed a murine polytrauma model with TBI and fracture to evaluate healing in a controlled system. Fractures were created both contralateral and ipsilateral to the TBI to test whether differential responses of humoral and/or neuronal systems drove altered healing patterns. Our results show increased bone formation after TBI when injuries occur contralateral to each other, rather than ipsilateral, suggesting a role of the nervous system based on the crossed neuroanatomy of motor and sensory systems. Analysis of the humoral system shows that blood cell counts and inflammatory markers are differentially modulated by polytrauma. A data-driven multivariate analysis integrating all outcome measures showed a distinct pathological state of polytrauma and co-variations between fracture, TBI and systemic markers. Taken together, our results suggest that a contralateral bone fracture and TBI alter the local neuroinflammatory state to accelerate early fracture healing. We believe applying a similar data-driven approach to clinical polytrauma may help to better understand the complicated pathophysiological mechanisms of healing.

Split immunity: immune inhibition of rat gliomas by subcutaneous exposure to unmodified live tumor cells.

Gliomas that grow uninhibited in the brain almost never metastasize outside the CNS. The rare occurrences of extracranial metastasis are usually associated with a suppressed immune system. This observation raises the possibility that some gliomas might not grow outside the CNS due to an inherent immune response, We report in this study that the highly malignant F98 Fischer rat undifferentiated glioma, which grows aggressively in the brain, spontaneously regresses when injected live s.c. We found that this regression is immune-mediated and that it markedly enhances the survival or cures rats challenged with the same tumor intracranially either before or after the s.c. live-cell treatment. Adoptive transfer experiments showed the effect was immune-mediated and that the CD8 T cell fraction, which exhibited direct tumor cytotoxicity, was more effective than the CD4 T cell fraction in mediating resistance to intracranial challenge of naive rats. Brain tumors from treated rats exhibited enhanced CD3(+)CD8(+)CD4(-) and CD3(+)CD4(+)CD8(-) T cell infiltration and IFN-γ secretion. The results in the F98 glioma were corroborated in the Lewis rat CNS-1 astrocytoma. In both tumor models, s.c. treatment with live cells was significantly better than immunization with irradiated cells. We propose in this study a location-based immunotherapeutic phenomenon we term "split immunity": a tumor that thrives in an immune-privileged site may be inhibited by injecting live, unmodified tumor cells into a site that is not privileged, generating protective immunity that spreads back to the privileged site. Split immunity could explain several long-standing paradoxes regarding the lack of overt extracranial metastasis in patients with primary brain tumors.

T cell vaccination induces the elimination of EAE effector T cells: analysis using GFP-transduced, encephalitogenic T cells.

T cell vaccination (TCV) with irradiated encephalitogenic T cells induces resistance to EAE. However, the fate of the encephalitogenic T cells in vivo following TCV has yet to be studied. Here we used anti-MBP encephalitogenic T cells that were transduced to express GFP to study the effects of TCV on these cells. In naïve rats or in control-vaccinated (Ova-GFP) rats injected i.v. with GFP-labeled effector cells, high numbers of effector T cells were found along with macrophages, CD8 T cells and Non-GFP CD4 cells in the spleens, parathymic lymph nodes (PTLN) and spinal cords. In contrast, the recipients that had been treated with TCV (anti-MBP T-cell lines) showed few if any GFP-labeled effector T cells throughout the disease (day 1-8) and their spinal cords were almost clear of macrophages, CD4 and CD8 cells. Splenocytes in the control groups secreted IFNgamma in response to MBP and showed high numbers of IFNgamma secreting CD4 and CD8 cells in their spinal cords at the disease peak. In the TCV-protected groups, splenocytes showed no reactivity to MBP but secreted IFNgamma in response to irradiated encephalitogenic T cells--an anti-idiotypic response. Thus, TCV leads to a marked decrease in the numbers of effector T cells in the CNS and lymphoid organs, to a marked reduction in the Th1 cytokine producing cells in the CNS, and to the appearance of T cells responsive to the anti-MBP effector T cells.

T-cell seeding: neonatal transfer of anti-myelin basic protein T-cell lines renders Fischer rats susceptible later in life to the active induction of experimental autoimmune encephalitis.

Fischer strain rats resist active induction of experimental autoimmune encephalomyelitis (EAE) following immunization with guinea-pig myelin basic protein (MBP) in complete Freund's adjuvant (CFA). Nevertheless, we now report that an encephalitogenic CD4(+) anti-MBP T-cell line could be developed from actively immunized Fischer rats. Adoptive transfer of the activated line mediated acute EAE in adult Fischer rats, but not in 1-day-old rats. Moreover, we found that both resting and activated anti-MBP T cells injected 1 day post-natally rendered these rats susceptible later in life to the active induction of EAE by immunization with MBP/CFA. The actively induced EAE manifested the accelerated onset of a secondary, memory-type response. Resting anti-MBP T cells injected even up to 2 weeks post-natally produced no clinical signs but seeded 50-100% of the recipients for an active encephalitogenic immune response to MBP. An earlier T-cell injection (1-2 days) produced a higher incidence and stronger response. The transferred resting T cells entered the neonatal spleen and thymus and proliferated there but did not change the total anti-MBP precursor number in adults. Splenocytes harvested from rats that were injected neonatally but not exposed to MBP in vivo proliferated strongly and produced significant amounts of interferon-gamma to MBP in vitro. Similar results were observed in rats injected with resting T-cell lines reactive to ovalbumin, suggesting that the neonatal injection of resting T cells specific for a self or for a foreign antigen can seed the immune system with the potential for an enhanced effector response to that antigen later in life.