Enlarged memory T-cell pool and enhanced Th1-type responses in chronic myeloid leukemia patients who have successfully discontinued IFN-α monotherapy

PLoS One. 2014 Jan 31;9(1):e87794. doi: 10.1371/journal.pone.0087794. eCollection 2014.


A small proportion of chronic myeloid leukemia patients treated with interferon-α (IFN-α) monotherapy are able to discontinue the treatment without disease relapse although residual leukemia cells are present. Recently, we showed that these patients have increased amount of NK-cells and a distinct blood cytokine profile. We now aimed to study the function of NK- and T-cells in order to understand the role of the immune system in maintaining the treatment response after IFN-α discontinuation. The study included 13 patients: 5 patients were still treated with IFN-α monotherapy (IFN-ON, median treatment time 163 months) and 8 had stopped the treatment successfully (IFN-OFF, median time without therapy 42 months). Detailed immunophenotype and cytokine production of NK- and T-cells was analyzed with flow cytometry. In addition, the cytotoxicity of NK-cells was studied using K562 as target cells and both the degranulation and direct killing was measured. Compared to healthy controls, IFN-OFF patients had increased proportion of CD4(+) effector memory (CCR7(-)CD45RA(-); median 23% vs. healthy 16%, p = 0.009) and CD8(+) central memory T-cells (CCR7(+)CD45RA(-); median 26% vs. healthy 14%, p = 0.004). Further, upon stimulation the IFN-γ/TNF-α cytokine secretion by CD4(+) T-cells was significantly enhanced in IFN-OFF patients (median 13.7% vs. healthy 7.8%, p = 0.01), and CD4+ effector and central memory cells were the main cytokine producers. No similar increase was observed in IFN-ON group (6.5%). In addition, the proportion of NK-cells was significantly increased in IFN-OFF patients (median IFN-OFF 24%, healthy 13%, p = 0.04), but their direct killing of K562 cells was impaired. The cytotoxicity of NK-cells was also diminished in IFN-ON patients. To conclude, in addition to elevated NK-cell count, IFN-OFF patients have increased amount of memory T-cells, which are able to induce strong cytokine response upon stimulation. This activity may contribute to the maintenance of prolonged remission after successful IFN-α discontinuation.

Publication types

  • Clinical Trial
  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • CD4 Lymphocyte Count
  • Female
  • Humans
  • Immunologic Factors / administration & dosage*
  • Immunologic Memory / drug effects*
  • Interferon-alpha / administration & dosage*
  • K562 Cells
  • Killer Cells, Natural / immunology
  • Killer Cells, Natural / metabolism
  • Killer Cells, Natural / pathology
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / blood
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / drug therapy*
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / immunology
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / pathology
  • Male
  • Middle Aged
  • Th1 Cells / immunology*
  • Th1 Cells / metabolism
  • Th1 Cells / pathology


  • Immunologic Factors
  • Interferon-alpha

Grant support

This work was supported by the Finnish special governmental subsidy for health sciences, research and training, by the Finnish Cancer Societies, Academy of Finland, Blood Disease Foundation, Finnish Association of Haematology, Sigrid Juselius Foundation and grant LF-2013-004. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.