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Updated: Jun 26, 2026
Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury
Published on: September 4, 2013
Macrophage subsets in mechanical brain injury (MBI)--a contribution to timing of MBI based on immunohistochemical
1Institute of Legal Medicine, University Hospital Schleswig-Holstein, Germany. moehmichen@gmx.de
Abstract:
Cortical hemorrhages as a consequence of closed mechanical brain injury (MBI) trigger an inflammatory response including a distinct increase of macrophages. According to published data this reactive macrophage population is heterogenous as to their immunological properties. The expression of certain immunohistochemically detectable epitopes of macrophages, however, may correlate with the posttraumatic interval (PTI). In a pilot study, 50 selected cases of cortical hemorrhages with 1 min to 1.5 years PTI were examined by light microscopy and macrophages were labeled with CD68-, HLA-D-, HAM-56-, LN-5-, and 25F9-antibodies, while hemosiderin was detected by a Prussian-blue reaction. Qualitative and semiquantitative investigations were performed. The semiquantitative study included 5 different classes. The results of the study revealed a distinct timetable of the appearance of macrophages labeled with certain antibodies. While HLA-D immunoreactivity was detected after a PTI of 6h in the cortex and white matter bordering the traumatic hemorrhage, CD68 immunopositive macrophages were present after 12h, LN-5 and HAM-56 after 48h, and 25F9 within 10d. Hemosiderin-containing macrophages were detectable within 100h in the same region. Within the hemorrhage itself a certain immunoreactivity of macrophages starts several hours before: CD68 after 3h, LN-5 after 24h, HAM-56 after 31h, hemosiderin after 76h, and 25F9 after 4d. For forensic purposes these observations are of crucial importance because the time course of the appearance of certain immunopositive macrophages labeled with different antibodies allows a differentiated timing of contusional injuries; however, the cause of this different immunopositive reaction remains unexplained. The observed time dependency of different macrophage antigen expressions in cortical hemorrhages after closed head injury is a suitable method to estimate the PTI and will allow a forensic reliable estimation if future investigations are extended on higher numbers of cases and/or additional markers.
Insights
Forensic timing of brain injuries is enhanced by tracking macrophage markers. Different macrophage immunopositive reactions appear at distinct times after cortical hemorrhages, aiding in posttraumatic interval estimation.
Area of Science:
- Neuropathology
- Forensic Medicine
- Immunohistochemistry
Background:
- Closed mechanical brain injury (MBI) causes cortical hemorrhages and triggers inflammation with diverse macrophage populations.
- Macrophage immunological properties and antigen expression may correlate with the posttraumatic interval (PTI).
Purpose of the Study:
- To investigate the temporal expression of macrophage markers in cortical hemorrhages following MBI.
- To determine if specific macrophage immunopositive reactions can reliably estimate the PTI for forensic applications.
Main Methods:
- Pilot study of 50 cortical hemorrhage cases with PTI from 1 minute to 1.5 years.
- Light microscopy and immunohistochemistry using CD68, HLA-D, HAM-56, LN-5, and 25F9 antibodies.
- Detection of hemosiderin using Prussian-blue reaction; qualitative and semiquantitative analysis.
Main Results:
- Distinct timetables for macrophage marker appearance were observed in both surrounding tissue and hemorrhage core.
- HLA-D appeared by 6h, CD68 by 12h, LN-5/HAM-56 by 48h, 25F9 by 10d, and hemosiderin by 100h in surrounding tissue.
- Earlier appearance noted within the hemorrhage: CD68 (3h), LN-5 (24h), HAM-56 (31h), hemosiderin (76h), 25F9 (4d).
Conclusions:
- The time-dependent expression of macrophage antigens in cortical hemorrhages after MBI is a viable method for estimating PTI.
- These findings are crucial for forensic purposes, allowing differentiated timing of contusional injuries.
- Further research with larger case numbers and additional markers is needed for forensic reliability.
