Suppression by thimerosal of ex-vivo CD4+ T cell response to influenza vaccine and induction of apoptosis in primary memory T cells

PLoS One. 2014 Apr 1;9(4):e92705. doi: 10.1371/journal.pone.0092705. eCollection 2014.


Thimerosal is a preservative used widely in vaccine formulations to prevent bacterial and fungal contamination in multidose vials of vaccine. Thimerosal was included in the multidose non-adjuvanted pandemic 2009 H1N1 vaccine Panenza. In the context of the analysis of the ex-vivo T cell responses directed against influenza vaccine, we discovered the in vitro toxicity Panenza, due to its content in thimerosal. Because thimerosal may skew the immune response to vaccines, we investigated in detail the ex-vivo effects of thimerosal on the fate and functions of T cells in response to TCR ligation. We report that ex-vivo exposure of quiescent or TCR-activated primary human T cells to thimerosal induced a dose-dependent apoptotic cell death associated with depolarization of mitochondrial membrane, generation of reactive oxygen species, cytochrome c release from the mitochondria and caspase-3 activation. Moreover, exposure to non-toxic concentrations of thimerosal induced cell cycle arrest in G0/G1 phase of TCR-activated T cells, and inhibition of the release of proinflammatory cytokines such as IFN gamma, IL-1 beta, TNF alpha, IL-2, as well as the chemokine MCP1. No shift towards Th2 or Th17 cells was detected. Overall these results underline the proapoptotic effect of thimerosal on primary human lymphocytes at concentrations 100 times less to those contained in the multidose vaccine, and they reveal the inhibitory effect of this preservative on T-cell proliferation and functions at nanomolar concentrations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Apoptosis / drug effects*
  • CD4-Positive T-Lymphocytes / immunology*
  • Caspase 3 / metabolism
  • Cell Cycle Checkpoints / drug effects
  • Cell Proliferation / drug effects
  • Cells, Cultured
  • Chemokines / metabolism
  • Cytochromes c / metabolism
  • Dose-Response Relationship, Immunologic
  • Enzyme Activation / drug effects
  • Humans
  • Immunologic Memory / drug effects*
  • Influenza A Virus, H1N1 Subtype / drug effects
  • Influenza A Virus, H1N1 Subtype / immunology
  • Influenza Vaccines / immunology*
  • Lymphocyte Activation / drug effects
  • Membrane Potential, Mitochondrial / drug effects
  • Mitochondrial Membrane Transport Proteins / drug effects
  • Mitochondrial Membrane Transport Proteins / metabolism
  • Mitochondrial Permeability Transition Pore
  • Reactive Oxygen Species / metabolism
  • Receptors, Antigen, T-Cell / metabolism
  • Thimerosal / toxicity*


  • Chemokines
  • Influenza Vaccines
  • Mitochondrial Membrane Transport Proteins
  • Mitochondrial Permeability Transition Pore
  • Reactive Oxygen Species
  • Receptors, Antigen, T-Cell
  • panenza vaccine
  • Thimerosal
  • Cytochromes c
  • Caspase 3

Grant support

This work was supported by grants from the French Ministry of Health (Programme Hospitalier de Recherche Clinique (PHRC) National), ANRT (Agence Nationale de la Recherche et de la Technologie) and Institut Pasteur. Crossject Company and ANRT provided the academic research/private research partnership to fund a CIFRE PhD fellowship to Emily Loison. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.