PR1-specific cytotoxic T lymphocytes are relatively frequent in umbilical cord blood and can be effectively expanded to target myeloid leukemia

Cytotherapy. 2016 Aug;18(8):995-1001. doi: 10.1016/j.jcyt.2016.05.007.


Background aims: PR1 is an HLA-A2 restricted leukemia-associated antigen derived from neutrophil elastase and proteinase 3, both of which are normally stored in the azurophil granules of myeloid cells but overexpressed in myeloid leukemic cells. PR1-specific cytotoxic lymphocytes (PR1-CTLs) have activity against primary myeloid leukemia in vitro and in vivo and thus could have great potential in the setting of adoptive cellular therapy (ACT). Adult peripheral blood-derived PR1-CTLs are infrequent but preferentially lyse myeloid leukemia cells. We sought to examine PR1-CTLs in umbilical cord blood (UCB) because UCB units provide a rapidly available cell source and a lower risk of graft-versus-host disease, even in the setting of mismatched human leukocyte antigen (HLA) loci.

Methods: We first determined the frequency of PR1-CTLs in HLA-A2(+) UCB units and then successfully expanded them ex vivo using repeated stimulation with PR1 peptide-pulsed antigen-presenting cells (APCs). After expansion, we assessed the PR1-CTL phenotype (naive, effector, memory) and function against PR1-expressing target cells.

Results: PR1-CTLs are detected at an average frequency of 0.14% within the CD8(+) population of fresh UCB units, which is 45 times higher than in healthy adult peripheral blood. UCB PR1-CTLs are phenotypically naive, consistent with the UCB CD8(+) population as a whole. In addition, the cells can be expanded by stimulation with PR1 peptide-pulsed APCs. Expansion results in an increased frequency of PR1-CTLs, up to 4.56%, with an average 20-fold increase in total number. After expansion, UCB PR1-CTLs express markers consistent with effector memory T cells. Expanded UCB PR1-CTLs are functional in vitro as they are able to produce cytokines and lyse PR1-expressing leukemia cell lines.

Conclusions: This study is the first report to show that T cells specific for a leukemia-associated antigen are found at a significantly higher frequency in UCB than adult blood. Our results also demonstrate specific cytotoxicity of expanded UCB-derived PR1-CTLs against PR1-expressing targets. Together, our data suggest that UCB PR1-CTLs could be useful to prevent or treat leukemia relapse in myeloid leukemia patients.

Keywords: PR1; antigen specific cytotoxic T lymphocyte; leukemia; umbilical cord blood.

MeSH terms

  • Adult
  • Antibody-Dependent Cell Cytotoxicity*
  • Cells, Cultured
  • Fetal Blood / cytology*
  • Fetal Blood / immunology
  • HLA-A2 Antigen / chemistry
  • HLA-A2 Antigen / immunology*
  • HLA-A2 Antigen / metabolism
  • Humans
  • Immunotherapy, Adoptive*
  • K562 Cells
  • Leukemia, Myeloid / immunology
  • Leukemia, Myeloid / therapy*
  • Lymphocyte Count
  • Myeloblastin / chemistry
  • Myeloblastin / immunology*
  • Myeloblastin / metabolism
  • T-Lymphocytes, Cytotoxic / immunology*
  • T-Lymphocytes, Cytotoxic / metabolism
  • U937 Cells


  • HLA-A2 Antigen
  • Myeloblastin