A Novel Cyclopropenyl Fatty Acid Library Reveals Tissue-Specific Preferences for Regulatory T Cell Uptake Through Click-Chemistry

Immune function is critically dependent on the nutrient microenvironment, of which fatty acids are central. Tools are lacking to quantify fatty acid uptake at the single-cell level, which has hindered understanding how primary immune cells use them in physiological settings. Here we show the synthesis and utilization of novel cyclopropenyl-fatty acids (cpFA) of different saturation and chain length, that can be detected by click chemistry. We validated that CpFA are compatible with downstream omics pipelines and thus could be used to determine phenotypic links to relative uptake. Using cpFA, we found that CD4 ⁺ regulatory T cells increase arachidonic acid uptake selectively in the intestine. RORγt ⁺ Tregs possessed superior Cp-arachidonic acid uptake in the mesenteric lymph node, compared to the small intestine, suggesting cell-intrinsic and niche factors control arachidonic acid uptake. CpFA are therefore a key technological advancement in immunometabolism that can reveal FA preferences of immune cells in tissues at the single cell level.