Impaired natural killer cell phenotype and function in idiopathic and heritable pulmonary arterial hypertension

Circulation. 2012 Aug 28;126(9):1099-109. doi: 10.1161/CIRCULATIONAHA.112.110619. Epub 2012 Jul 25.


Background: Beyond their role as innate immune effectors, natural killer (NK) cells are emerging as important regulators of angiogenesis and vascular remodeling. Pulmonary arterial hypertension (PAH) is characterized by severe pulmonary vascular remodeling and has long been associated with immune dysfunction. Despite this association, a role for NK cells in disease pathology has not yet been described.

Methods and results: Analysis of whole blood lymphocytes and isolated NK cells from PAH patients revealed an expansion of the functionally defective CD56(-)/CD16(+) NK subset that was not observed in patients with chronic thromboembolic pulmonary hypertension. NK cells from PAH patients also displayed decreased levels of the activating receptor NKp46 and the killer immunoglobulin-like receptors 2DL1/S1 and 3DL1, reduced secretion of the cytokine macrophage inflammatory protein-1β, and a significant impairment in cytolytic function associated with decreased killer immunoglobulin-like receptor 3DL1 expression. Genotyping patients (n=222) and controls (n=191) for killer immunoglobulin-like receptor gene polymorphisms did not explain these observations. Rather, we show that NK cells from PAH patients exhibit increased responsiveness to transforming growth factor-β, which specifically downregulates disease-associated killer immunoglobulin-like receptors. NK cell number and cytotoxicity were similarly decreased in the monocrotaline rat and chronic hypoxia mouse models of PAH, accompanied by reduced production of interferon-γ in NK cells from hypoxic mice. NK cells from PAH patients also produced elevated quantities of matrix metalloproteinase 9, consistent with a capacity to influence vascular remodeling.

Conclusions: Our work is the first to identify an impairment of NK cells in PAH and suggests a novel and substantive role for innate immunity in the pathobiology of this disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Animals
  • CD56 Antigen / analysis
  • Chemokine CCL4 / metabolism
  • Cytotoxicity, Immunologic / drug effects
  • Extracellular Matrix / metabolism
  • Female
  • GPI-Linked Proteins / analysis
  • Genotype
  • Humans
  • Hypertension, Pulmonary / etiology
  • Hypertension, Pulmonary / genetics
  • Hypertension, Pulmonary / immunology*
  • Immunophenotyping
  • Killer Cells, Natural / chemistry
  • Killer Cells, Natural / drug effects
  • Killer Cells, Natural / immunology*
  • Killer Cells, Natural / pathology
  • Male
  • Matrix Metalloproteinase 9 / analysis
  • Mice
  • Mice, Inbred C57BL
  • Middle Aged
  • Natural Cytotoxicity Triggering Receptor 1
  • Pulmonary Embolism / complications
  • Random Allocation
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, IgG / analysis
  • Receptors, KIR2DL1 / biosynthesis
  • Receptors, KIR2DL1 / genetics
  • Receptors, KIR3DL1 / biosynthesis
  • Receptors, KIR3DL1 / genetics
  • Receptors, KIR3DS1 / biosynthesis
  • Receptors, KIR3DS1 / genetics
  • Transforming Growth Factor beta / pharmacology


  • CD56 Antigen
  • Chemokine CCL4
  • FCGR3B protein, human
  • GPI-Linked Proteins
  • NCAM1 protein, human
  • NCR1 protein, human
  • Natural Cytotoxicity Triggering Receptor 1
  • Receptors, IgG
  • Receptors, KIR2DL1
  • Receptors, KIR3DL1
  • Receptors, KIR3DS1
  • Transforming Growth Factor beta
  • Matrix Metalloproteinase 9