Background: Dendritic cells (DCs) rely on tightly coordinated metabolic programs to support their immune functions. Amino acid availability is increasingly recognized as a critical determinant of immune cell fate. Threonine (Thr) is an essential amino acid and key substrate for one-carbon metabolism, however, its role in shaping DC biology remains unexplored.
Methods: We investigated the role of Thr in DC biology using ex vivo splenic DCs and in vitro-derived Flt3L BMDCs under Thr-replete and Thr-deplete RPMI. Maturation markers and cytokine production were measured using flow cytometry following LPS-OVA stimulation.
Results: We found that DCs stimulated in the absence of Thr show limited immunogenic maturation, with reduced co-stim marker expression and cytokine (IL-12 and TNFa) production. Flt3L-derived BMDCs differentiated in Thr-deficient RPMI results in significantly lower yield of cDC1s and pDCs. We found that the absence of Thr significantly reduced H3K4me3 and global histone methylation in cDCs, implicating Thr in the maintenance of active transcriptional programs that support DC differentiation and effector functions. Strikingly, Thr restriction phenocopies treatment with the EZH2 inhibitor Tazemetostat and the dual EZH1/2 inhibitor Valemetostat, linking Thr availability to PRC2-dependent epigenetic regulation.
Conclusions: These data establish Thr as essential for DC differentiation and immune functions and suggest a functional link between Thr availability and PRC2-mediated epigenetic programming in cDCs. Ongoing studies are investigating how Thr-dependent histone methylation shapes DC transcriptional identity and DC-mediated T cell priming.