Intraarticular glucocorticoid (GC) treatment of rheumatoid arthritis (RA) patients ( n = 15) decreases synovial expression of F95 and peptidylarginine deiminase 4 (PAD4) but not PAD2. Hematoxylin-eosin (HTX-EOS) staining illustrates the histologic pattern of frozen synovial biopsy sections of an RA patient before (a) and after (b) intraarticular GC treatment. Brown diaminobenzidine immunoperoxidase staining shows a significant decrease in the expression of citrullinated proteins, as detected by F95 antibody (c, before treatment; d, after treatment), no changes in PAD2 expression as detected by either ROI001 (f, before treatment; g, after treatment) antibody or SN665 antibody (i, before treatment; j, after treatment) and a significant decrease in PAD4 expression, as detected by SG1467 antibody (o, before treatment; p, after treatment) but not by SN823 antibody (l, before treatment; m, after treatment). Original magnification, ×100; insets show close-up details from the same samples. Graphs show results of semiquantitative analysis on a 4-grade scale for citrullinated proteins (e), PAD2 as detected with either ROI001 (h) or SN665 (k) antibody, and PAD4 as detected with either SN823 (n) or SG1467 (q) antibody. Values represent the median, and whiskers, the range (*P < 0.05).