Vessel-Specific Toll-Like Receptor Profiles in Human Medium and Large Arteries

TLDR

Inflammatory vasculopathies such as vasculitides and atherosclerosis exhibit tissue‑specific tropism for particular vascular beds, yet the mechanisms that direct wall inflammation to specific anatomic sites remain unclear. The study aimed to determine whether six major human arteries differ in their capacity to initiate innate and adaptive immune responses by comparing pathogen‑sensing and T‑cell–stimulatory functions. Using gene‑expression profiling of TLR1–9, immunohistochemistry, and human‑SCID mouse chimera experiments, the authors identified vessel‑specific TLR expression patterns, dendritic cells at the media‑adventitia junction as key pathogen sensors, and demonstrated that conditioned dendritic cells could trigger T‑cell–mediated wall inflammation. The results showed that dendritic cells dominate pathogen sensing, T cells exhibit vessel‑specific activation profiles, and distinct TLR fingerprints confer differential responsiveness (e.g., iliac versus subclavian vessels to TLR5), indicating that each macrovascular bed has a unique immune signature that may dictate vessel‑specific risk for inflammatory vasculopathies.

Abstract

Background— Inflammatory vasculopathies, ranging from the vasculitides (Takayasu arteritis, giant cell arteritis, and polyarteritis nodosa) to atherosclerosis, display remarkable target tissue tropisms for selected vascular beds. Molecular mechanisms directing wall inflammation to restricted anatomic sites within the vascular tree are not understood. We have examined the ability of 6 different human macrovessels (aorta and subclavian, carotid, mesenteric, iliac, and temporal arteries) to initiate innate and adaptive immune responses by comparing pathogen-sensing and T-cell–stimulatory capacities. Methods and Results— Gene expression analysis for pathogen-sensing Toll-like receptors (TLRs) 1 to 9 showed vessel-specific profiles, with TLR2 and TLR4 ubiquitously present, TLR7 and TLR9 infrequent, and TLR1, TLR3, TLR5, TLR6, and TLR8 expressed in selective patterns. Experiments with vessel walls stripped of the intimal or adventitial layer identified dendritic cells at the media-adventitia junction as the dominant pathogen sensors. In human artery–severe combined immunodeficiency (SCID) mouse chimeras, adoptively transferred human T cells initiated vessel wall inflammation if wall-embedded dendritic cells were conditioned with TLR ligands. Wall-infiltrating T cells displayed vessel-specific activation profiles with differential production of CD40L, lymphotoxin-α, and interferon-γ. Vascular bed–specific TLR fingerprints were functionally relevant, as exemplified by differential responsiveness of iliac and subclavian vessels to TLR5 but not TLR4 ligands. Conclusions— Populated by indigenous dendritic cells, medium and large human arteries have immune-sensing and T-cell–stimulatory functions. Each vessel in the macrovascular tree exhibits a distinct TLR profile and supports selective T-cell responses, imposing vessel-specific risk for inflammatory vasculopathies.