Liston Tissue Treg Nur77 (UbCre MHCIIflox)

The purpose of this series of experiments was two-fold: 1) Assess TCR activity in tissue-resident Tregs by means of Nur77 staining. 2) Assess whether loss of MHCII in all cells (via tamoxifen-inducible Cre under the ubiquitin promoter) would lead to a reduction in Nur77 expression in tissue Tregs, a change in their numbers within tissues or a change in their activation status. Conclusion: For the first aim, we conclude that tissue-resident Tregs show engagement of the TCR as determined by the Nur77 proxy. This Nur77 staining is higher in CD69+ (longer residency) Tregs than in CD69- Tregs. This analysis was performed using the WT controls. For the second aim, the results were inconclusive. The loss of MHCII was incomplete and slightly variable from one experiment to the next. In some experiments, we saw the expected outcome of reduced Nur77 and/or CD69 expression, but not consistently across all experiments. MHCII is expressed at such a high level that there is likely considerable protein still around in the absence of new transcription for quite some time. We were unable to administer tamoxifen for long enough to overcome this under our animal protocol. Nur77 FMO samples are provided