Marginal zone B cells control follicular helper T cell response to high cholesterol diet

Splenic innate-like marginal zone B (MZB) cells are strategically positioned at the interface between the circulating blood and lymphoid tissue, where they initiate rapid immune responses to blood-borne antigens. Here, we find that selective genetic deletion of MZB cells substantially increases the follicular helper T (Tfh) cell and germinal center (GC) response to high cholesterol diet (HCD), which leads to T cell-dependent acceleration of atherosclerosis. We show that MZB cells activate a homeostatic program in response to HCD, in which upregulation of the transcription factor Atf3 plays a determinant regulatory role. Shuttling of MZB cells to the follicle is dispensable for their regulatory properties on Tfh cells. Instead, HCD promotes increased interaction between MZB and (pre-)Tfh cells outside the follicle, and upregulates MZB cell expression of Cd274 in an Atf3-dependent manner. Interaction between MZB and Tfh cells leads to Cd274-mediated suppression of Tfh cell motility, limits Tfh cell accumulation in the follicle and suppresses the pro-atherogenic Tfh/GC response. Our findings reveal a previously unsuspected role for MZB cells in the control of Tfh/GC response to a cholesterol diet, and uncover a new mechanism through which MZB cells can couple their unique metabolic and innate immune properties and use them to maintain a tolerogenic state. The results may have broad (patho)physiological implications. Overall design: Transcriptomic comparision between high-fat diet and standard chow in LDLr -/- splenic marginal zone B cells

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Nus M, Sage AP, Lu Y, Masters L, Lam BYH, Newland S, Weller S, Tsiantoulas D, Raffort J, Marcus D, Finigan A, Kitt L, Figg N, Schirmbeck R, Kneilling M, Yeo GSH, Binder CJ, de la Pompa JL, Mallat Z