Figure 4: Id1 overexpression leads to an immunosuppressive phenotype and T-cell suppression.

Flow cytometry analysis of spleens from mice transplanted with Id1-overexpressing and control vector-transduced Lin⁻ BM cells for (a) absolute numbers of regulatory T cells (T-regs; CD4⁺CD25⁺Foxp3⁺; unpaired t-test, ^***P<0.001), for (b) ROS production, as determined by mean fluorescence intensity levels of dichlorofluorescein (DCF), a ROS-sensitive dye (unpaired t-test, ^***P<0.001). (c) CD8⁺ antigen-specific T-cell proliferation functional assessment of GFP⁺ CD11b⁺ Gr1⁺ splenocytes from Id1-overexpressing and control vector animals co-cultured with OT-I splenocytes in the presence of OVA_257–264 peptide. (analysis of variance, ^**P<0.01, *P<0.05). (d) OT-I T-cell proliferation expressed as suppression induced by GFP⁺ CD11b⁺ Gr1⁺ splenocytes from Id1-overexpressing and control vector animals, relative to the no MDSC control wells. Data expressed as percentage T-cell suppression compared with no MDSC control (unpaired t-test, *P<0.05). (e) Analysis of splenocytes from Id1-overexpressing mice and OT-II CD4+ T-cell co-cultures in the presence of OVA_323–329 peptide for IFNγ levels (unpaired t-test, *P<0.05) and (f) IL-10 levels compared with splenocytes from control vector-treated mice and OT-II CD4⁺ T-cell co-cultures (unpaired t-test, *P<0.05). Four independent experiments were performed.