B cell-guided inflammatory cascade perpetuates ICI-mediated colitis.

B cells with gut-homing markers and proinflammatory functions are increased at the asymptomatic stage in mice and patients susceptible to ICI-colitis.

• Why it matters: Understanding the mechanisms that predict ICI-colitis is crucial because current therapeutic options are limited and the onset mechanisms are unclear, hindering early intervention.
• What they did: The study analyzed circulating B cells in mice and patients, finding an increase in gut-homing, antigen-presenting, and cytokine-producing B cells at the asymptomatic stage, and demonstrated that B cell absence reduces pathogenic T cells and colitis in mice.
• The result: B cell dysregulation may serve as a biomarker for toxicity risk and a target for preventing ICI-colitis, with latent microbial dysbiosis potentially underlying B cell dysfunction.