Elevated circulating memory T cells precede immunotherapy toxicities in melanoma

Immune checkpoint inhibitor (ICI) therapy for cancer is limited by inflammatory toxicities that can be fatal. Predicting who will develop these toxicities is a critical clinical problem. Lozano et al. found that circulating CD4+ memory T cells and T cell receptor (TCR) diversity correlate with the risk of ICI toxicity, suggesting an important role for CD4+ memory T cells in the initiation of these inflammatory adverse events.