PTGDR and peritonitis: Recently, we found DP1 deficiency in macrophages led to M1 polarization and delayed resolution in zymosan‐induced peritonitis in mice (Kong et al, 2016, 2017), and deletion of the DP1 receptor in macrophages (DP1F/F/LysMCre) aggravated DSS‐induced colitis (Fig 4D–F).