Survival-time dependent increase in neuronal IL-6 and astroglial GFAP expression in fatally injured human brain tissue

Knowledge on trauma survival time prior to death following a lethal traumatic brain injury (TBI) may be essential for legal purposes. Immunohistochemistry studies might allow to narrow down this survival interval. The biomarkers interleukin-6 (IL-6) and glial fibrillary acidic protein (GFAP) are well known in the clinical setting for their usability in TBI prediction. Here, both proteins were chosen in forensics to determine whether neuronal or glial expression in various brain regions may be associated with the cause of death and the survival time prior to death following TBI. IL-6 positive neurons, glial cells and GFAP positive astrocytes all concordantly increase with longer trauma survival time, with statistically significant changes being evident from three days post-TBI (p < 0.05) in the pericontusional zone, irrespective of its definite cortical localization. IL-6 staining in neurons increases significantly in the cerebellum after trauma, whereas increasing GFAP positivity is also detected in the cortex contralateral to the focal lesion. These systematic chronological changes in biomarkers of pericontusional neurons and glial cells allow for an estimation of trauma survival time. Higher numbers of IL-6 and GFAP-stained cells above threshold values in the pericontusional zone substantiate the existence of fatal traumatic changes in the brain with reasonable certainty.