IgG1 Plasma Cells as Predictive Biomarkers for PD-1 Immunotherapy in Oncology

A recent study found that PD-1 immunotherapy response is strongly associated with intratumoral IgG1-producing plasma cells and concordant circulating IgG1 antibodies—signals that may refine patient selection and perioperative planning in surgical oncology.

In the study, investigators analyzed matched tumor and blood samples from patients treated with PD-1 inhibitors to assess objective responses and immune specificity against tumor antigens. The team combined transcriptomic and proteomic profiling with spatial and clonal analyses to link intratumoral immune phenotypes to circulating antibody signatures.

Expanded intratumoral IgG1 plasma cells and circulating IgG1 antibodies that recognize tumor-specific proteins define a tumor-targeted humoral response that complements PD-1–mobilized T-cell activity. The patterns include clonal expansion of preexisting B cell clones and blood antibodies binding cancer-testis and other tumor-associated antigens—consistent with coordinated antigen-specific immunity. Patients with concordant intratumoral and circulating IgG1 signatures also show stronger tumor-directed T-cell responses, indicating a multi-lineage immune architecture linked to clinical benefit. This combined footprint could improve predictive accuracy for PD-1 therapy by adding a humoral dimension to established T-cell–based biomarkers.