Apolipoprotein AI prevents regulatory to follicular helper T cell switching during atherosclerosis.

Gaddis, Dalia E; Padgett, Lindsey E; Wu, Runpei; McSkimming, Chantel; Romines, Veronica; Taylor, Angela M; McNamara, Coleen A; Kronenberg, Mitchell et al. · Nat Commun · 2018

basic_science · Level V

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Abstract

Regulatory T (Treg) cells contribute to the anti-inflammatory response during atherogenesis. Here we show that during atherogenesis Treg cells lose Foxp3 expression and their immunosuppressive function, leading to the conversion of a fraction of these cells into T follicular helper (Tfh) cells. We show that Tfh cells are pro-atherogenic and that their depletion reduces atherosclerosis. Mechanistically, the conversion of Treg cells to Tfh cells correlates with reduced expression of IL-2Rα and pSTAT5 levels and increased expression of IL-6Rα. In vitro, incubation of naive T cells with oxLDL prevents their differentiation into Treg cells. Furthermore, injection of lipid-free Apolipoprotein AI (ApoAI) into ApoE<sup>-/-</sup> mice reduces intracellular cholesterol levels in Treg cells and prevents their conversion into Tfh cells. Together our results suggest that ApoAI, the main protein in high-density lipoprotein particles, modulates the cellular fate of Treg cells and thus influences the immune response during atherosclerosis.

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