The mouse macrophage or monocyte–macrophage lineage marker F4/80, also known in the rat as epidermal growth factor-like module-containing mucin-like hormone receptor-like 1 (EMR1), can be used as a marker of both monocyte influx and resident peritoneal macrophages.1,78 Here we showed increased recognition of anti-ICAM-1 MBs ex vivo by CD11b + EMR1 + macrophages from a rat peritonitis model. This evidence concerns the gene ADGRE1 and peritonitis.