Cell-type source of CRS-associated cytokine in the lymph nodes. ISH was used to identify cells expressing IL-6 (A,C) and interferon-γ (B). (D) Lack of IL-6 (green) and CD3 (red) colocalization indicates that T cells/CARTs are not the source of IL-6. (E) Colocalization of IL-6 (green) with von Willebrand factor (vWF; red) expressed by blood vessel endothelium and (F) lymphatic vessel endothelial antigen 1 (LYVE1; red) confirms that endothelial cells, in particular blood vessel endothelial cells, are the key source of IL-6 in CRS. Inset: high-power view of the double-positive endothelial cells.