IL21R and infection: Despite effective bacterial replication and significantly higher bacterial burden in Il21r-/- mice, histology demonstrated only a moderate increase in inflammatory cell recruitment, predominantly in the mucosa, and mild hyperplasia accompanied with loss of goblet cells in the distal colons of Il21r-/- mice 9 days after infection with C. rodentium, the time of peak infection when bacterial loads are not significantly different between WT and Il21r-/- mice (Fig 1A–1C).