Soluble Programmed Death 1 (PD-1) Is Decreased in Patients With Immune Thrombocytopenia (ITP): Potential Involvement of PD-1 Pathway in ITP Immunopathogenesis

Clin Appl Thromb Hemost. 2016 Apr;22(3):248-51. doi: 10.1177/1076029614562952. Epub 2014 Dec 14.


Immune thrombocytopenia (ITP) is an autoimmune disease characterized by dysregulation of T cells. Programmed death (PD) 1 and programmed death 1 ligand 1 (PD-L1) are cosignaling molecules, and the major role of the PD-1 pathway is the inhibition of self-reactive T cells and to protect against autoimmune diseases. We measured levels of serum soluble PD 1 (sPD-1) and serum soluble PD-L1 (sPD-L1) in 67 patients with ITP (24 newly diagnosed ITP [ndITP], 43 chronic ITP [cITP]) and 21 healthy controls (HCs). We determined decreased serum sPD-1 levels both in patients with ndITP and in patients with cITP when compared to HC. Moreover, there was a positive correlation between sPD-1 levels and platelet counts. The sPD-L1 levels were decreased in patients with ndITP when compared to patients with cITP. This is the first study investigating PD-1 signaling pathway in ITP. Decreased sPD-1 levels may have a role in ITP pathogenesis as without the inhibitory regulation of PD-1, sustained activation of T cells may cause inflammatory responses which is the case in ITP.

Keywords: programmed death 1; programmed death 1 ligand 1; thrombocytopenia.

MeSH terms

  • Adult
  • Aged
  • Chronic Disease
  • Female
  • Humans
  • Male
  • Middle Aged
  • Platelet Count
  • Programmed Cell Death 1 Receptor / blood*
  • Programmed Cell Death 1 Receptor / immunology
  • Purpura, Thrombocytopenic, Idiopathic / blood*
  • Purpura, Thrombocytopenic, Idiopathic / diagnosis
  • Purpura, Thrombocytopenic, Idiopathic / immunology
  • Signal Transduction / immunology
  • Solubility


  • PDCD1 protein, human
  • Programmed Cell Death 1 Receptor