Immunohistochemical distribution of S-100 protein in the cerebral cortex with regard to the cause of death in forensic autopsy.

S-100 protein (S100) is an acidic calcium-binding protein, which is abundantly found in the brain. The aim of the present study was to investigate the immunohistochemical distribution of S100 in the cerebral cortex in forensic autopsy cases with regard to the cause of death and relationship to its serum levels. The cases (n = 286, 3-48 h postmortem) included fatal head injuries (n = 89), acute death from other blunt injuries (n = 29), sharp instrument injuries (n = 20), asphyxiation (n = 29: strangulation/hanging, n = 22; aspiration, n = 7), drownings (n = 22), fire fatalities (n = 68), cerebrovascular diseases (n = 9) and acute myocardial infarction/ischemia (AMI, n = 20). S100-immunopositivity was mainly observed in the gliacytes, in part, in the neurons and myelins. For S100B-immunostaining, the gliacytes and myelins were positive, whereas the neurons were negative. Positivity in astrocytes was dependent on the cause of death, and was significantly lower in acute deaths due to strangulation/hanging and drowning, and mildly low in those due to injuries. Positivity in neurons and myelins was frequently observed in delayed head injury deaths and fire fatalities, showing an inverse relationship with the positivity in astrocytes in head injury cases. For cases of acute death, there was an inverse relationship between S100-positivity in the astrocytes and the serum S100B level. These observations suggest that astrocytes are more rapidly and severely injured than neurons during fatal brain damage, thereby causing an elevation in the serum S100B level.