Pretreatment of moDCs by the JAK2 inhibitor TG101348 blocks IL-6–induced pSTAT3 but does not impair moDC-stimulatory potency. (A) Contour plots depict STAT3 phosphorylation evaluated in immature moDCs with or without rhuIL-6 (5000 IU/mL), treated with the JAK2 inhibitor TG101348 (1μM) or DMSO control (0.01%). (B) Bar graphs depict the means of the gated percentages of moDCs with pSTAT3 in panel A ± SD from 3 independent experiments; *P < .05 by paired t test. (C) Graphs demonstrate T-cell proliferation measured by a colorimetric assay in an allogeneic MLR of T cells stimulated by TG101348 or DMSO-pretreated, cytokine-matured moDCs (DC:T 1:30). Dotted line represents T cells alone. Stimulation index equals optical density (OD) of allogeneic MLR divided by the OD of T cells alone. Scatter plot and bar graph show average of triplicate means from 4 independent experiments ± SEM. NS indicates not significant by paired t test. TG101348 must be present during initial T-cell encounters with allogeneic moDCs to inhibit alloreactive T-cell proliferation. (D-E) IL-6–induced phosphorylation of STAT3 in resting T cells is depicted, mirroring the exact same conditions as used in panels A and B; n = 5; *P < .05 by paired t test. (F) Graphs show T-cell proliferation determined by colorimetric assay in 5-day allogeneic MLRs, with DMSO (0.01%) control or TG101348 (1μM) added directly to the culture once on day 0. Neither the T cells nor cytokine-matured moDCs were pretreated. DC:T ratios vary from 1:30 to 1:1000. Dotted line represents T cells alone. Stimulation indices were calculated for DC:T 1:30 groups, OD of allogeneic MLR divided by OD of T cells alone. Scatter plot and bar graph show average triplicate means ± SEM from 4 independent experiments. **P = .001-.01 by paired t test of area under the curve.