FOXP3 and systemic mastocytosis: In both UM and SM patients, Foxp3 expression was higher in TNFRII+ Treg cells (combined median MFI: 56 [IQR: 32–103]) compared to TNFRII− Treg cells (combined median MFI: 41 [IQR: 32–63]); p = 0.04; Figure 2C.