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Allograft inflammatory factor-1/Ionized calcium-binding adapter molecule 1 is specifically expressed by most
1Institute II of Anatomy, University of Cologne, Joseph Stelzmann Strasse 9, 50931, Cologne, Germany. c.koehler@uni-koeln.de
Abstract:
Ionized calcium-binding adapter molecule 1 (Iba1) is a 147-amino-acid calcium-binding protein widely in use as a marker for microglia. It has actin-crosslinking activity and is involved in aspects of motility-associated rearrangement of the actin cytoskeleton. The Iba1 gene and protein are identical to allograft inflammatory factor-1 (AIF-1), a protein involved in various aspects of inflammation, which was investigated independently from Iba1. Although regarded to be monocyte/macrophage-specific, expression by germ cells in testis showed that AIF-1/Iba1 is not exclusively expressed by cells of the monocyte/macrophage lineage. Furthermore, AIF-1 was found in cells not belonging to the monocyte/macrophage lineage under pathological conditions. Here, the distribution of AIF-1/Iba1 in the normal mouse has been examined, by immunohistochemistry, to determine whether AIF-1/Iba1 expression is confined to macrophages and spermatids. Spermatids are the only cells not belonging to the monocyte/macrophage lineage found to express AIF-1/Iba1 in the normal mouse, by this method. This study has not demonstrated AIF-1/Iba1 expression in dendritic cells, although this protein might be expressed by subsets of dendritic cells. AIF-1/Iba1 can be regarded a "pan-macrophage marker" because, except for alveolar macrophages, all subpopulations of macrophages examined express AIF-1/Iba1.
Insights
Ionized calcium-binding adapter molecule 1 (Iba1), also known as allograft inflammatory factor-1 (AIF-1), is a pan-macrophage marker. In normal mice, AIF-1/Iba1 is expressed by macrophages and spermatids, but not dendritic cells.
Area of Science:
- Immunology and Cell Biology
- Neuroscience
- Inflammation Research
Background:
- Ionized calcium-binding adapter molecule 1 (Iba1) is a protein commonly used as a microglia marker.
- Iba1 shares identity with allograft inflammatory factor-1 (AIF-1), a protein implicated in inflammatory processes.
- AIF-1/Iba1 has been considered specific to monocytes/macrophages, but its expression in other cell types is noted.
Purpose of the Study:
- To investigate the distribution of AIF-1/Iba1 in normal mouse tissues.
- To determine if AIF-1/Iba1 expression is exclusively limited to macrophages and spermatids.
- To clarify the specificity of AIF-1/Iba1 as a marker for myeloid lineage cells.
Main Methods:
- Immunohistochemistry was employed to examine AIF-1/Iba1 distribution.
- Analysis focused on various macrophage subpopulations and other cell types in normal mouse tissues.
- Expression patterns were compared between myeloid and non-myeloid cell populations.
Main Results:
- AIF-1/Iba1 was confirmed to be expressed across most macrophage subpopulations, supporting its role as a pan-macrophage marker.
- Spermatids were identified as the sole non-monocyte/macrophage cell type expressing AIF-1/Iba1 in normal mice.
- No AIF-1/Iba1 expression was detected in dendritic cells by this method, though potential subset expression was acknowledged.
Conclusions:
- AIF-1/Iba1 serves as a reliable pan-macrophage marker, with notable exceptions like alveolar macrophages.
- The expression of AIF-1/Iba1 in spermatids indicates its presence beyond the classical monocyte/macrophage lineage.
- Further investigation may be warranted to explore potential AIF-1/Iba1 expression in specific dendritic cell subsets.
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