Staining of HLA-DR, Iba1 and CD68 in human microglia reveals partially overlapping expression depending on cellular
Debbie A E Hendrickx1, Corbert G van Eden1, Karianne G Schuurman1
1Neuroimmunology Research Group, Netherlands Institute for Neuroscience, Meibergdreef 47, 1105 BA Amsterdam, The Netherlands.
Abstract:
HLA-DR, Iba1 and CD68 are widely used microglia markers in human tissue. However, due to differences in gene regulation, they may identify different activation stages of microglia. Here, we directly compared the expression of HLA-DR, Iba1 and CD68 in microglia with different phenotypes, ranging from ramified to amoeboid, to foamy phagocytizing macrophages, in adjacent sections immunocytochemically double stained for two of the markers. Material was used from patients diagnosed with multiple sclerosis (MS) and Alzheimer's disease (AD) patients and control subjects because together they contain all the microglia activation stages in an acute and a chronic inflammatory setting. We found a similar, yet not identical, overall expression pattern. All three markers were expressed by ramified/amoeboid microglia around chronic active MS lesions, but overlap between HLA-DR and Iba1 was limited. Foamy macrophages in the demyelinating rims of active MS lesions of MS expressed more HLA-DR and CD68 than Iba1. All markers were expressed by small microglia accumulations (nodules) in MS NAWM. Dense core AD plaques in the hippocampus were mostly associated with microglia expressing HLA-DR. Diffuse AD plaques were not specifically associated with microglia at all. These results indicate that microglia markers have different potential for neuropathological analysis, with HLA-DR and CD68 reflecting immune activation and response to tissue damage, and Iba1 providing a marker more suited for structural studies in the absence of pathology.
Insights
Human microglia markers HLA-DR, Iba1, and CD68 show distinct expression patterns in neurological diseases. HLA-DR and CD68 reflect immune activation, while Iba1 is better for structural analysis.
Area of Science:
- Neuroscience
- Immunology
- Pathology
Background:
- Microglia are key immune cells in the central nervous system.
- Human microglia markers like HLA-DR, Iba1, and CD68 are crucial for neuropathological studies.
- These markers may represent different microglial activation states due to varying gene regulation.
Purpose of the Study:
- To directly compare the expression of HLA-DR, Iba1, and CD68 in microglia with diverse phenotypes.
- To evaluate the utility of these markers across different activation stages and disease contexts (MS and AD).
Main Methods:
- Adjacent tissue sections from multiple sclerosis (MS), Alzheimer's disease (AD) patients, and controls were used.
- Immunocytochemical double staining was performed for pairs of markers (HLA-DR, Iba1, CD68).
- Microglia phenotypes ranged from ramified to amoeboid and foamy phagocytizing macrophages.
Main Results:
- All three markers were expressed by microglia around chronic active MS lesions, but HLA-DR and Iba1 overlap was limited.
- Foamy macrophages in active MS lesions showed higher HLA-DR and CD68 expression compared to Iba1.
- Microglia nodules in MS normal appearing white matter expressed all three markers.
- Dense core plaques in AD hippocampus were associated with HLA-DR expressing microglia, while diffuse plaques were not specifically associated.
Conclusions:
- Microglia markers HLA-DR and CD68 are indicative of immune activation and tissue damage response.
- Iba1 is more suitable for structural studies of microglia, especially in non-pathological contexts.
- The choice of microglia marker depends on the specific research question in neuropathology.
