Altered Purinergic Signaling and CD8+ T Cell Dysregulation in STAT3 GOF Syndrome.

Signal transduction downstream of activating stimuli controls CD8+ T cell biology, however these external inputs can become uncoupled from transcriptional regulation in Primary Immune Regulatory Disorders (PIRDs). Gain-of-function (GOF) variants in STAT3 amplify cytokine signaling and cause a severe PIRD characterized by early onset autoimmunity, lymphoproliferation, recurrent infections, and immune dysregulation. In both primary human and mouse models of STAT3 GOF, CD8+ T cells have been implicated as pathogenic drivers of autoimmunity. The molecular mechanisms by which STAT3 GOF variants drive this pathology remain unclear. We found that naive CD8+ T cells have an increased capacity for IFN-g and TNF-a secretion. Given this dysregulation of CD8+ T cell function, we evaluated changes in immunoregulatory pathways and found evidence of dysregulated purinergic signaling via high dimensional immune profiling, single-cell RNA sequencing, and functional assessment. Specifically, while expression of CD39, which transforms ATP to AMP, was increased on CD8+ T cells from patients with STAT3 GOF, downstream purinergic family members, CD73 and the adenosine receptor, A2AR, were downregulated, impairing the potential to produce or sense inhibitory adenosine. Patients with STAT3 GOF can be clinically treated with JAK inhibitors, and this partially normalized naive CD8+ T cell dysregulation, including aberrant cytokine production. The extent of normalization scaled with normalization of CD73 and A2AR. This suggests that a dysregulated purinergic signaling axis plays an important role in CD8+ T cell dysregulation in STAT3 GOF, which may have implications for other inflammatory disorders with amplified STAT signaling.