Beyond T cell toxicity-Intrathecal chemokine C-X-C motif ligand indicating B cell involvement in immune-related adverse events following checkpoint inhibition: A two-case series and literature review.

The case observations highlight the plethora of uncertainties in diagnosis and treatment of ICI-associated nirAE, exemplify the heterogeneity of immune mechanisms involved, and suggest a role of B cells, which may be underdiagnosed. Intrathecal CXCL13 may serve as a biomarker of B cell involvement in nirAE, supported by intrathecal immunoglobulin synthesis, presence of plasma cells, and/or recruitment of cognate immune cells.