Abstract
BACKGROUND: Accumulating evidence indicates that iron oxide nanoparticles modulate immune responses, and induce oxidative stress in macrophages. It was recently reported that iron oxide nanoparticles attenuated antigen-specific immunity in vivo, though the underlying mechanism remains elusive. The present study investigates the direct effect of iron oxide nanoparticles on antigen-specific cytokine expression by T cells, and potential underlying mechanisms. METHODS: Ovalbumin-primed splenocytes were exposed to iron oxide nanoparticles, followed by restimulation with ovalbumin. Cell viability, cytokine production, and cellular levels of glutathione and reactive oxygen species were measured. RESULTS: The splenocyte viability and the production of interleukin-2 and interleukin-4 were unaffected, whereas interferon-γ production was markedly attenuated by iron oxide nanoparticles (10-100 μg iron/mL) in a concentration-dependent manner. Iron oxide nanoparticles also transiently diminished the intracellular level of glutathione, with a peak response at 6 hours posttreatment. The effects of iron oxide nanoparticles on interferon-γ and glutathione were attenuated by the presence of N-acetyl-L-cysteine, a precursor of glutathione. However, iron oxide nanoparticles did not influence the generation of reactive oxygen species. CONCLUSION: Iron oxide nanoparticles induced a differential effect on antigen-specific cytokine expression by T cells, in which the T helper 1 cytokine IFN-γ was sensitive, whereas the T helper 2 cytokine interleukin-4 was refractory. In addition, the suppressive effect of iron oxide nanoparticles on interferon-γ was closely associated with the diminishment of glutathione.