Related Experiment Video
Updated: Aug 1, 2026
3D Modeling of the Lateral Ventricles and Histological Characterization of Periventricular Tissue in Humans and Mouse
Published on: May 19, 2015
Variability of laminin immunoreactivity in human autopsy brain
S Mori1, N H Sternberger, M M Herman
1Department of Neurology, University of Maryland School of Medicine, Baltimore 21201.
Insights
Postmortem proteolysis unmasks laminin antigen in brain tissue, similar to enzymatic digestion. This unmasking can also occur through tissue damage during cryostat sectioning of fresh brain samples.
Area of Science:
- Neuroscience
- Immunohistochemistry
- Proteomics
Background:
- Laminin immunoreactivity is often masked in formalin-fixed brain sections.
- Proteolytic treatment is typically required to reveal laminin antigen in fixed tissues.
Purpose of the Study:
- To investigate the masking of laminin immunoreactivity in formalin-fixed brain sections.
- To analyze the effect of postmortem delay on laminin antigen unmasking.
- To compare antigen unmasking in human and rat brain tissues.
Main Methods:
- Analysis of frozen and formalin-fixed human autopsy brains at various postmortem intervals.
- Examination of unfixed frozen sections and formalin-fixed vibratome sections.
- Investigation of rat brains processed with and without postmortem delay.
Main Results:
- Intense laminin immunoreactivity was observed in unfixed frozen sections of both human and rat brains.
- Formalin fixation did not diminish immunoreactivity in unfixed sections.
- In fixed vibratome sections, immunoreactivity varied with postmortem delay and was enhanced by tissue damage.
Conclusions:
- Postmortem proteolysis effectively unmasks laminin antigen, mimicking enzymatic digestion.
- Tissue damage during cryostat sectioning can also induce laminin antigen unmasking.
- Understanding these processes is crucial for accurate immunohistochemical analysis of laminin in brain tissue.
Abstract:
Laminin immunoreactivity is thought to be masked in formalin-fixed sections since proteolytic treatment is required to unmask it. We analyzed this masking with frozen and formalin-fixed human autopsy brains obtained at various postmortem periods. In unfixed, frozen sections, intense immunoreactivity was invariably detected in vascular walls of entire sections. When such sections were postfixed in formalin, immunoreactivity was not diminished even after prolonged fixation. In vibratome sections of brain fixed in formalin in situ, immunoreactivity varied with postmortem delay: in most cases, immunoreactivity was weak and restricted to superficial cortical layers. However, the extent of immunoreactivity increased with postmortem delay. Two cases fixed after prolonged postmortem periods revealed moderate immunoreactivity throughout the sections. We also investigated rat brains processed without postmortem delay. In unfixed frozen sections, immunoreactivity again was observed throughout the sections, independent of the length of any postfixation. In vibratome sections of fixed rat brain, immunoreactivity was restricted to the cutting margins of the brain blocks and around a trauma-induced cortical lesion, regardless of how long the blocks had been kept in fixative. Our data suggest that postmortem proteolysis accomplishes similar unmasking of laminin antigen as digestion on paraffin sections and that such unmasking can also be effected by proteolysis induced by damaging tissue during cryostat sectioning of fresh tissue.
