Photographs of microglia cells in the olfactory bulb 2 days after a standardized transection of the olfactory bulb sectioned and stained with Iba-1.

<p>These photomicrographs are showing the cells advancing. (A and B): Stage 1A, a microglia cell has processes that are ramified and spread out, with a small soma. (C–D): Stage 2A, the soma has increased in size to approximately 1.5–2 times the soma diameter of a stage 1A cell. The cell processes have started to retreat and the branches next to the cell soma are thickened. (E–F): Stage 3A, the cell soma diameter is enlarged to 2–3 times the soma diameter of stage 1A. All cell processes have retracted and thickened. (G–H): Stage 4A, the soma diameter is 3–4 times larger than the stage 1 soma; all thin cell processes have completely retracted and only the thick cell branches remain. (I–J): Stage 5A, soma diameter is 5 times larger than the soma diameter in stage 1; the thick process is replaced by a thin process oriented in the direction of the cell movement. All branches are gone. (K–L): Stage 6A shows the transformation from microglia to macrophage. The microglia cell has a large round morphology with a large soma, with one short or no processes. (Scale bar: 10 µm).