Figure 2

(a) Percentage change (relative to sham-irradiated animals) in the number of Iba1⁺ mucosal macrophages at 24 hours, 1 week, 6 weeks, 18 weeks, and 30 weeks post-irradiation. An increase in infiltrating macrophages is not seen until 6 weeks after irradiation, with most of the animals exhibiting an increase in the number of mucosal macrophages. This remains unchanged over time, indicating a state of long-lasting, possibly chronic mucosal inflammation. (b–e) Iba1⁺-expressing macrophages visualised with DAB immunohistochemistry in the irradiated colorectal mucosa at various time-points after irradiation. Macrophages are still abundant in the mucosa 30 weeks after irradiation and tend to aggregate around the blood vessels, close to the degenerating crypts, and under the epithelial surface (arrows). Scale bars, 50 μm. (f) CD31⁺ blood vessels in irradiated animals, shown in terms of the percentage change relative to the sham-irradiated animals. The increase in blood vessels at 30 weeks after irradiation suggests late, compensatory angiogenesis. ^#The data for the 6-week group have been published previously⁹.