A lot of antibodies that have been raised against modified Histones, e.g. methylated or acetylated histones, do not seem to have been tested for their specificity. Antibodies against mono-methylated lysines should, for instance, not recognize di- or tri-methylated sites. Or totally different sites which might be methylated as well. Eglehofer et al. reported about the specificity of > 200 antibodies against 57 different Histone modifications and found that more than 25% failed in specificity tests (Nat Struct Mol Biol 18.1, 91-3 ). In their paper they advised rigorous testing and provided an Antibody Validation Database.