Receptor-type protein tyrosine phosphatase gamma (PTPγ), a new identifier for myeloid dendritic cells and specialized macrophages

Protein tyrosine phosphatase (PTPγ) is a receptor-like molecule with a known role in murine hematopoiesis. We analyzed the regulation of PTPγ expression in the human hematopoietic system, where it was detected in human peripheral blood monocytes and dendritic cells (DCs) of myeloid and plasmacytoid phenotypes. Its expression was maintained during in vitro monocyte differentiation to dendritic cells (moDC) and was further increased after maturation with bacterial lipopolysaccharide (LPS), CD40L, and TNFα. But PTPγ was absent when monocytes from the same donor were induced to differentiate in macrophages. B and T lymphocytes did not express PTPγ. Rather, PTPγ mRNA was expressed in primary and secondary lymphoid tissues, and the highest expression was in the spleen. PTPγ was detected by immunohistochemistry in subsets of myeloid-derived DCs and specialized macrophages (tingible bodies, sinus and alveolar macrophages). Classic macrophages in infective or reactive granulomatous reactions did not express PTPγ. Increased PTPγ expression was associated with a decreased ability to induce proliferation and interferon-γ secretion in T cells by moDCs from patients with advanced pancreatic cancer. Taken together, these results indicate that PTPγ is a finely regulated protein in DC and macrophage subsets in vitro and in vivo.