B cell subsets are associated with durable responses in distinct cancer types after immune checkpoint inhibition.

Germinal center and memory B cells are enriched in favorable-prognosis cohorts, while immunoglobulin A–positive plasma cells are enriched in unfavorable-prognosis cohorts across 12 tumor types after immune checkpoint inhibition.

• Why it matters: The study addresses how B cells and antibody responses relate to cancer survival, which remains understudied despite their role in adaptive immunity.
• What they did: In a prospective randomized phase 2 trial of 106 patients on immune checkpoint inhibitors, intratumoral B cells were profiled by single-cell RNA sequencing from 152 patients across 12 tumor types, and B-cell depletion with rituximab before surgery was used to assess effects on intratumoral T cells.
• The result: B cells are linked to durable complete responses in certain cancer types and are associated with improved long-term overall survival even when T cell infiltrates are already high, supporting a coordinated T cell–B cell adaptive response.