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A new immunoperoxidase marker for microglia in paraffin section
1Department of Pathology (Neuropathology), Cleveland Clinic Foundation, Ohio 44106.
Abstract:
We tested antisera against monocytic and lymphocytic lineages on 27 formalin-fixed, paraffin-embedded brains, obtained at autopsy, using the avidin-biotin-complex immunoperoxidase method. Patients ranged from one day to 69 years with 12 cases under the age of two. LN-1-positive microglia were present in 22 brains. LN-1 did not stain any other glial or neuronal cells. Five negative brains included two irradiated gliomas, two cases of multiple sclerosis and one normal case. Immunostaining was confined to cells with bipolar processes and rod-shaped nuclei recapitulating the characteristic features of microglia in silver-impregnated sections. LN-1-positive microglia were most prominent in the grey matter and in the grey-white junction with fewer positive cells seen in the white matter. Double immunostaining with LN-1 and glial fibrillary acidic protein (GFAP) clearly distinguished LN-1-positive microglia and GFAP-positive astrocytes. The expression of LN-1, a B-lymphocyte antigen, by microglia contradicts the macrophage derivation theory and supports data indicating a functional role of microglia in immune processes. LN-1, while not specific for microglia, should be considered a useful marker, more reliable than silver impregnation, for detecting microglia in paraffin section.
Insights
The LN-1 antibody identifies microglia in brain tissue, supporting their role in immune responses. This marker is more reliable than traditional silver staining for detecting microglia in paraffin-embedded sections.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia are the primary immune cells of the central nervous system.
- Their precise lineage and markers for identification in tissue sections have been subjects of research.
- Understanding microglial markers is crucial for studying neuroinflammation and neurological diseases.
Purpose of the Study:
- To evaluate the utility of the LN-1 antibody as a marker for microglia.
- To compare LN-1 staining with traditional silver impregnation methods.
- To investigate the potential immune cell lineage of microglia.
Main Methods:
- Tested antisera against monocytic and lymphocytic lineages on 27 autopsy-obtained formalin-fixed, paraffin-embedded brain samples.
- Employed the avidin-biotin-complex immunoperoxidase method for immunostaining.
- Utilized double immunostaining with LN-1 and glial fibrillary acidic protein (GFAP) to differentiate microglia from astrocytes.
Main Results:
- LN-1-positive microglia were identified in 22 out of 27 brains, particularly in grey matter and grey-white junctions.
- Immunostaining revealed cells with characteristic microglial morphology (bipolar processes, rod-shaped nuclei).
- LN-1 staining successfully distinguished microglia from GFAP-positive astrocytes.
Conclusions:
- The expression of LN-1, a B-lymphocyte antigen, by microglia challenges the macrophage derivation theory.
- Findings support a functional role for microglia in immune processes within the brain.
- LN-1 is a useful and reliable marker for detecting microglia in paraffin sections, outperforming silver impregnation.