Introduction:
Dendritic cells (DCs) that are known as professional antigen-presenting cells have been found to pre-locate in non-inflammatory arterial wall and increasingly accumulate during atherosclerosis progression. Previous findings suggested that residential DCs in the intima are responsible for capturing modified lipids and forming foam cells during the initiation of atherosclerosis.
Hypothesis:
DC accumulation and enhanced DC-T cell interaction play a critical role in the initiation of atherosclerosis.
Methods:
We measured plaque formation, vascular DC accumulation and antigen-specific T cell proliferation mediated by isolated aortic cells in ApoE-/- mice, as well as DTR-CD11c/ApoE-/- or DTR-CD11b/ApoE-/- mice for conditional depletion of DCs or macrophages, respectively. A brief high-fat diet for 10 days was used as a model of initial atherosclerosis.
Results:
In addition to increased intimal DC accumulation and plaque formation in aortic roots, 10 days of HFD induced T cell infiltration in ApoE-/- mice, compared to those without HFD as the control. Isolated aortic cells from mice with 10-day HFD showed stronger capability in inducing antigen-specific T cell proliferation, compare to the control (HFD: 3.14±0.71%; no HFD: 1.56±0.36%; p=0.022). Single diphtheria toxin (DT) injection at day 1 yielded approximately 50% decrease in intimal DC accumulation, as well as 60% attenuation in plaque formation in DTR-CD11c/ApoE-/- mice after 10-day HFD. Capability of stimulating antigen-specific T cell proliferation was also impaired in aortic cells from DC-depleted mice (DT-treated: 1.62±0.30%; PBS-treated: 3.04±0.59%; p= 0.004), along with reduction in indirect conduction of T cell activation. In contrast, no significant changes were found in plaque formation and DC accumulation in DT-injected DTR-CD11b/ApoE-/- mice after 10 days of HFD, compared to control group. Furthermore, depletion of CD11b+ macrophages in either aortas or spleens didn’t alter capability of inducing antigen-specific T cell proliferation in DT-injected mice.
Conclusions:
These results suggested that vascular DCs rather than macrophages play a more important role in T cell activation and initiation of atherosclerosis.
PD-1 suppresses TCR-CD8 cooperativity during T-cell antigen recognition