ID2 and plasma cell myeloma: At physiological concentrations (e.g., serum butyrate: ~2-5 μM in oxaliplatin responders, 69), SCFAs boost cytotoxic immunity via HDAC inhibition: 2 μM butyrate enhances natural killer (NK) cell cytotoxicity against myeloma by inducing extracellular vesicles and reducing IL-10 (69); 1–2 mM butyrate/10 μM acetate potentiates CD8+ T cells—butyrate drives inhibitor of DNA binding 2 (ID2)-dependent IL-12 signaling to upregulate IFN-γ/granzyme B (70); acetate shifts TAMs to M1 via Acetyl-CoA Carboxylase 1-mediated fatty acid biosynthesis (71, 72).