Direct effects of carbon nanotubes on dendritic cells induce immune suppression upon pulmonary exposure

Abstract

Pharyngeal aspiration of single-walled carbon nanotubes (SWCNTs) caused inflammation, pulmonary damage, and an altered cytokine network in the lung. Local inflammatory response in vivo was accompanied by modified systemic immunity as documented by decreased proliferation of splenic T cells. Preincubation of naïve T cells in vitro with SWCNT-treated dendritic cells reduced proliferation of T cells. Our data suggest that in vivo exposure to SWCNT modifies systemic immunity by modulating dendritic cell function.

Figure 1

Transmission (A) and scanning (B) electron microscopic images of SWCNT.

Figure 2

Inflammatory response in the lung of mice after pharyngeal aspiration of SWCNT. Open bars – 1 day post exposure; closed bars – 7 days post exposure. Data are shown as means ± SEM (3 experiments, 6 animals/group); *p<0.05 vs. ^α p<0.05 vs. 40 μg/mouse SWCNT exposure, ^βp<0.05 vs. 1d post exposure.

Figure 3

Suppressed splenic T cell proliferation following pharyngeal aspiration of SWCNT. A – Proliferation index. B – Expansion index. C – Representative cell division profile from control animal. D - Representative cell division profile from SWCNT-exposed animal (120 μg/mouse). Data are shown as means ± SEM (2 experiments, 5 animals/group); *p<0.05 vs. control.

Figure 4

A typical TE micrograph illustrating internalization of SWCNT (arrow) by DC (in vitro) at 48h of exposure.

Figure 5

Co-culturing of T cells with SWCNT exposed DC suppresses the T cell proliferation response. A – Proliferation Index. B – Expansion Index. T cells were incubated for 48h with SWCNT-exposed DC, LPS-exposed DC, or LPS+SWCNT exposed DC. Following co-incubation, exposed DC were depleted and freshly generated DC were added as stimulatory cells. Responder T cell proliferation was measured in 48h. T cells co-incubated with SWCNT-exposed DC showed impaired proliferation. T cells co-incubated with LPS-exposed DC showed increased proliferation. Proliferation of T cells co-incubated with LPS+SWCNT-treated DC was decreased to the control levels. In other words, exposure to SWCNT abrogated the stimulatory effect of LPS on DC. Data are shown as means ± SEM (3 experiments); *p<0.05 vs. control, ^αp<0.05 vs. LPS exposure, ^βp<0.05 vs. 25 μg/ml SWCNT exposure.