Figure 5.

IL-6 neutralization impairs MDSCs in N3-tg mice. N3-tg mice were injected i.p. with neutralizing anti-IL-6 antibodies (anti-IL-6) or isotype controls (Ctr), twice a week and sacrificed/analyzed after 4 weeks of treatment; some of the mice were also injected i.p. with BrdU solution 1 day before the sacrifice. (A) The graph reports the ratio between the CD11b⁺Gr-1⁺ cell counts in anti-IL-6-treated N3-tg mice and in control mice, expressed as % of control, measured by FACS analysis in the BM and spleen (SPL) and presented as mean value ± SD from three independent experiments (n = 4 mice per group). (B) The percentages of Gr-1⁺BrdU1⁺ cells in the BM and SPL of anti-IL-6-treated N3-tg mice vs. controls are shown, assessed by FACS analysis. The data are presented as the mean value ± SD from two independent experiments (n = 3 mice per group). (C) Representative FACS analysis of suppression assay of CFSE-labeled/activated wt T splenocytes (“responders”), cultured either alone (no MDSC), as a control, or in combination with Gr-1⁺ MDSCs (“suppressors”), at the indicated MDSCs/responders ratio. Numbers inside cytograms indicate the percentages of proliferating wt CD4⁻CD8⁺ T responder cells. The Gr-1⁺ MDSCs were magnetically selected from spleen of N3-tg mice, treated with isotype control antibodies (MDSCs/Ctr) or anti-IL-6-neutralizing antibodies (MDSCs/anti-IL-6). In (D), the results of the same suppression test, as in (C), are illustrated as the percentage of proliferating CD4⁻CD8⁺ responder cells in MDSC-containing cultures (MDSCs/Ctr or MDSCs/anti-IL-6) and in control cultures set up in the absence of MDSCs (no MDSCs), at the indicated MDSCs:responders ratio. The results represent mean values ± SD from two independent experiments (n = 3 mice per group), with two technical replicates per experiment. ns, not significant, p > 0.05; ^* p ≤ 0.05; ^** p ≤ 0.01, ^*** p ≤ 0.001 represent significant differences between the indicated groups.