Abstract
Immune checkpoint inhibitors (ICI) have revolutionized cancer therapy, but their use is limited by the development of autoimmunity in healthy tissues as a side effect of treatment. Such immune-related adverse events (IrAE) contribute to hospitalizations, cancer treatment interruption and even premature death. ICI-induced autoimmune diabetes mellitus (ICI-T1DM) is a life-threatening IrAE that presents with rapid pancreatic beta-islet cell destruction leading to hyperglycemia and life-long insulin dependence. While prior reports have focused on CD8+ T cells, the role for CD4+ T cells in ICI-T1DM is less understood. Here, we identify expansion CD4+ T follicular helper (Tfh) cells expressing interleukin 21 (IL-21) and interferon gamma (IFNG) as a hallmark of ICI-T1DM. Furthermore, we show that both IL-21 and IFNG are critical cytokines for autoimmune attack in ICI-T1DM. Because IL-21 and IFNG both signal through JAK-STAT pathways, we reasoned that JAK inhibitors (JAKi) may protect against ICI-T1DM. Indeed, JAKi provide robust in vivo protection against ICI-T1DM in a mouse model that is associated with decreased islet-infiltrating Tfh cells. Moreover, JAKi therapy impaired Tfh cell differentiation in patients with ICI-T1DM. These studies highlight CD4+ Tfh cells as underrecognized but critical mediators of ICI-T1DM that may be targeted with JAKi to prevent this grave IrAE.