Density of iNOS- and Iba1-positive cells in the normal (
) and bacteria-challenged (
) olfactory mucosa (A). The density of iNOS-positive cells following bacterial exposure is significantly more than that in the unperturbed olfactory mucosa, increasing from 28 ± 2 to 129 ± 10 cells/mm mucosa. This resulting high density of iNOS-positive cells is greater than the density of Iba1-positive cells, indicating that a proportion of the iNOS-positive cells are not macrophages. Error bars represent SEM. **p < 0.01. The iNOS- and Iba1-positive cells are predominantly located in the lamina propria (LP), close to the olfactory epithelium (OE; B, C). In the normal, intact olfactory mucosa (D,E), Iba1-positive cells can occasionally be observed in the olfactory epithelium (arrow in E). Scale bar = 100 μm.