Figure 1.

CD8⁺ T‐cells lacking PTPN22 have sufficiently strong T‐cell receptor (TCR) signals to overcome transforming growth factor β (TGFβ)‐mediated suppression. (a) Control T‐cells stimulated through the TCR upregulate expression of transcription factors (TFs), activation markers such as CD25 and translocate NFAT into the nucleus within 24 hr. Subsequently, cells start to secrete IL‐2 and proliferate. (b) TGFβ added at the start of control cell culture inhibits TCR‐driven TFs, activation marker upregulation and NFAT translocation, resulting in lower levels of IL‐2 production, thereby less cell proliferation and more cell death by d3. (c) TCR stimulation is stronger in Ptpn22 ^−/− cells, resulting in more IL‐2 and more cell proliferation. (d) TGFβ is less able to suppress strong TCR signals, allowing Ptpn22 ^−/− cells to secrete enough IL‐2 to proliferate and survive by d3.