HDAC inhibition modulated histone acetylation and proinflammatory cytokine production after human allo-HCT. Triangles and black bars denote patients in the study who received vorinostat. Circles and open bars denote control patients who did not receive vorinostat. Median values ± interquartile range are plotted. Each data point in a dot plot represents a single patient. All plots include data from at least 2 independent experiments. (A) Levels of acetylated (Ac-) H3 and H4 30 and 100 days after allo-HCT. Levels in each patient normalized to β-actin. (B) Levels of interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), IL-6, and IL-8 in the plasma of study patients and control patients 14 days after allo-HCT. Control, n = 18; study, n = 31. (C) TNF-α and IL-6 production by PBMC after ex vivo stimulation with lipopolysaccharide (500 ng/mL) for 16 to 24 hours, 30 days after allo-HCT. Control, n = 12; study, n = 14. (D) Intracellular staining of IL1-β, TNF-α, and IL-6 in CD11c⁺ PBMCs of study and control patients 30 and 100 days after allo-HCT, after ex vivo stimulation with phorbol 12-myristate 13-acetate (PMA) and ionomycin. Day 30: control, n = 6; study, n = 10. Day 100: control, n = 6; study n = 6.