Figure 4.

Iba1-directed immunohistochemical labeling of the olfactory bulb. (A–C) Iba1-ir labeling of the control section shows quiescent ramified microglia in all OB layers. (D) Iba1-ir in the EAE section relative to lateral-to-medial OB axis; numerous Iba1⁺ cells were seen in the ONL on the lateral OB side. (E,F) Clusters of Iba1-ir cells belonging to infiltrated macrophages and highly reactive ovoid microglia in the ONL and GL. (G) Ramified microglia in the deeper OB layers. Microglia with a slightly reactive phenotype but organized in a non-overlapping manner in (H) EPL and (I) MCL and GCL. Confocal Iba1 immunofluorescence confirms the presence of ovoid Iba1-ir cells in (J) ONL and (K) GL, and typical ramified microglia with preserved domain organization in (L) EPL and GCL. (M) Graphs showing the number of reactive Iba1⁺ cells in distinct cell layers in EAE sections. Statistical significance: ****p < 0.0001. Scale bar: 1000 μm in (A,D); 100 μm in (B,C,E,F,G); 50 μm in (H,I); 20 μm in (J–L). GCL, granule cell layer; GL, glomerular layer; EPL, external plexiform layer; MCL, mitral cell layer; ONL, olfactory nerve layer.