PTPRZ1 and inflammatory bowel disease: This, together with the identification of a new receptor for IL-34: receptor-type protein-tyrosine phosphatase ζ (PTPRZ1, RPTP-ζ) [11], prompted us to investigate the intestinal expression profile of PTPRZ1. We show higher PTPRZ1 gene expression in colon compared to ileum in non-IBD subjects.