The effect of HDAC inhibitors Trichostatin A (TSA; A), apicidin (B), MC1293 (C) and MS-275 (D) on eosinophil apoptosis in the presence of GM-CSF (in B-D: 0.1 ng/ml). In (A) the black colums indicate the effect of TSA in the absence of GM-CSF. Apoptosis was assessed by flow cytometry measuring the relative DNA fragmentation. *P < 0.05, **P < 0.01 and ***P < 0.001 as compared with the respective control. Mean ± S.E.M., n = 5-6.