AIF1 and ileus: However, Iba1 was also used as a marker to quantify the total population of macrophages in the mouse jejunum and their responsiveness to systemic lipopolysaccharide treatment (Mikkelsen et al., 2017), and to assess resident macrophages in the small intestine muscularis externa in response to inflammation in a postoperative ileus model (Enderes et al., 2020).