In vivo silencing of TAK1 expression and activity in myeloid cells. Arthritic DBA/1 mice received a single intravenous injection (0.5 mg/kg) of either anti-TAK1 siRNAs or nontargeting control siRNAs, formulated as lipoplexes. At days 2, 4, and 6 after siRNA lipoplex injection, TAK1 protein expression and phosphorylation were determined in CD11b- and CD11c-positive cells by flow cytometry after staining and permeabilization of mononuclear cells from blood (A-C) and spleen (D-F). (A,D) Representative dot plots are shown for siCT- (left panels) and siTAK1- (right panels) injected mice, 6 days after vehicle administration. Gating was performed on mononuclear cells after exclusion of doublets and dead cells. Histograms show mean percentages of TAK1 and P-TAK1 expression within the gated phenotypic markers indicated, in either blood (B-C) and spleen (E-F), at days 2 (white and black), 4 (dark gray), and 6 (light gray) after injection with either siCT- (white bars) or siTAK1- (black and gray bars) lipoplexes. Mean of cumulative data from 2 independent experiments, with 2 mice enrolled in each group are presented.