Hyperacetylation of cellular proteins in rheumatoid arthritis synovial tissue. (a) Immunohistochemical staining of rheumatoid arthritis (RA) synovial tissue with antibodies against acetyl-lysine (Ac) (upper panels) and control rabbit antibodies (lower panels): 100× (left panels) and 400× (right panels) magnifications are displayed. (b) Immunofluorescent staining of RA synovial tissue (400× magnification) with anti-Ac antibodies (green) alone (upper panel) or in combination with 4',6-diamidino-2-phenylindole dihydrochloride staining (blue) (lower panel) showing localization to cellular nuclei. (c) Representative immunofluorescent double staining of RA synovial tissue with anti-Ac antibodies (green) and antibodies against cellular markers (red) for T lymphocytes (CD3), B lymphocytes (CD22), fibroblast-like synoviocytes (CD55), or synovial macrophages (CD68 and CD163). (d) Quantification of protein hyperacetylation in specific synovial cellular subsets. Double stainings were performed on RA synovial tissue and a minimum of 100 random cells positive for each CD marker assessed for hyperacetylation of nuclear proteins. Values represent the mean percentage and standard error of the mean of cells positive for each marker displaying protein hyperacetylation from four RA patients. Samples were obtained from patients fulfilling the American College of Rheumatology criteria for RA . Detailed descriptions of materials and methods used in these experiments have either been described elsewhere  or are available in Additional file 1.