CSF1 and inflammatory bowel disease: Our data supports the hypothesis that the expression of PTPRZ1 and CSF-1R together with the macrophage growth factors IL-34 and CSF-1 are important during inflammation of the gastro-intestinal tract, and lead to the suggestion that IL-34 may act as a local marker and potential therapeutic target in IBD, however this has to be confirmed with functional data in future studies.