Autoimmunity-associated protein tyrosine phosphatase PEP negatively regulates IFN-α receptor signaling.
Bottom Line: Pep(-/-) hematopoietic progenitors demonstrate increased IFNAR signaling, increased IFN-inducible gene expression, and enhanced proliferation and activation compared to Pep(+/+) progenitors in response to IFN-α.In addition, Pep(-/-) mice treated with IFN-α display a profound defect in hematopoiesis, resulting in anemia, thrombocytopenia, and neutropenia when compared to IFN-α-treated Pep(+/+) mice.As SLE patients carrying the PTPN22(C1858T) risk variant have higher serum IFN-α activity, these data provide a molecular basis for how type I IFNs and PTPN22 may cooperate to contribute to lupus-associated cytopenias.
Affiliation: Department of Immunology, Department of Translational Immunology, and Department of Pathology, Genentech, Inc., South San Francisco, CA 94080.Show MeSH
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Mentions: Since a type I IFN gene signature in peripheral blood mononuclear cells is associated with cytopenias in human lupus patients (Baechler et al., 2003), we further dissected the underlying pathogenesis and analyzed the effects of IFN-α on the hematopoietic progenitor compartment. Consistent with the previous description that Sca-1 is an IFN-α–induced activation marker (Essers et al., 2009), we observed increased Sca-1 expression on Pep+/+ cKit+ progenitors after IFN-α treatment (unpublished data). Although no differences in HSC and progenitor populations were observed between Pep+/+ and Pep−/− mice under homeostatic conditions (unpublished data), a significant reduction in HSC, multipotent progenitor (MPP2 and MPP3), megakaryocyte/erythrocyte progenitor (MEP), and myeloid progenitor (CMP and GMP) populations was observed in IFN-α5–treated Pep−/− mice compared to IFN-α5–treated Pep+/+ mice (Fig. 2, A and B). This effect was dose dependent, as administration of 10-fold less (108 PFU/mouse) Ad5-IFN-α5 did not affect the HSC population in Pep−/− mice, though the more differentiated multipotent progenitors (MPP2 and MPP3) and myeloid progenitors (CMP/GMP) populations were still reduced in IFN-α5–treated Pep−/− mice (Fig. 2, C and D). There was also a trend in the reduction of LS−K and MEP cells that did not reach statistical significance. Treatment with Ad5-IFN-α5 (108 PFU/mouse) did not result in mortality in either Pep+/+ or Pep−/− mice within a 60-d period (unpublished data). Similar effects were observed with administration of poly(I:C) with reduced cellularity in the more differentiated myeloid progenitors (MEP, CMP and GMP) in poly(I:C)-treated Pep−/− mice (Fig. 2, E and F). Consistent with enhanced progenitor activation, we observed increased Sca-1 expression on poly(I:C)-treated cKit+Pep−/− progenitors compared to Pep+/+ progenitors (Fig. 2 G). Together, these observations are consistent with increased activation and potential exhaustion of hematopoietic progenitors in Pep−/− mice after IFN-α treatment.
Affiliation: Department of Immunology, Department of Translational Immunology, and Department of Pathology, Genentech, Inc., South San Francisco, CA 94080.