Figure 1.

NIK upregulation impairs Treg suppressive function in vitro and in vivo. (a,b) iTregs: Purified NIKtg/Foxp3^RFP or WT/Foxp3^RFP CD4 Tconv were treated with TAT-Cre fusion protein to induce expression of the NIK transgene and were cultured under iTreg inducing conditions. Four days later, Foxp3^RFP+ iTreg cells were sorted and assessed for suppressive function against CFSE-labeled WT CD4⁺ Tconv. (a) Histograms depict CFSE intensity of gated WT CD4⁺ Tconv; numbers indicate percent of WT CD4 Tconv that have divided at least once. (b) X-axis indicates Treg: Tconv ratios; y-axis indicates percent of WT CD4⁺ Tconv that have divided at least once as determined by gating as in (a). (c,d) nTregs: CD4⁺RFP⁺ WT and NIKtg nTregs were sorted directly from spleens of mixed BM chimera recipients that had been reconstituted with equal numbers of NIKtg/CD4^Cre/Foxp3^RFP and WT/Thy1.1/Foxp3^RFP bone marrow cells. The sorted NIKtg and WT nTregs were assessed for suppressive function against WT CD4⁺ Tconv as in (a,b). (a–d) Data are from one representative experiment of 2; replicate data are shown in Supplementary Fig. S1. (e,f) Lungs from NIKtg/Foxp3^Cre and WT/Foxp3^Cre littermates were assessed for immunopathology by H&E staining. Data in (f) are pooled from 3 independent cohorts of mice; each data point represents the score of an individual mouse *p < 0.05.