19 maj 2026
Alberts et al. (BioRxiv)
Keywords
Plasma Cells (PCs)
Draining Lymph Node (dLN)
Triple-Negative Breast Cancer (TNBC)
Main Findings
Triple-negative breast cancer (TNBC) remains one of the most aggressive breast cancer subtypes lacking targetable hormone receptors and HER2 expression, and often shows limited responses to immune checkpoint blockade (ICB). While tertiary lymphoid structures and B cell rich microenvironments are often associated with favourable prognosis, the role of plasma cells (PCs) in cancer has remained controversial, with studies reporting both protective and tumour-promoting functions.
In this preprint, Alberts et al. (not peer reviewed), identify an unexpected antibody-independent immunosuppressive role for extrafollicular plasma cells (EF-PCs) accumulating within tumour-draining lymph nodes (td-LNs) in immune-cold TNBC.
Using the immune-cold 4T1.2 TNBC murine model, the authors observed marked PC hyperplasia within td-LNs. These PCs preferentially pervaded medullary cords and exhibited extrafollicular characteristics, including low somatic hypermutation, high proliferative capacity, and enrichment of MYC-associated transcriptional programs. Notably, their immunosuppressive function did not appear to depend on antibody production, as neither serum transfer nor Fcγ receptor blockade reversed tumour control following EF-PC depletion.
The authors further show that EF-PCs interfere with conventional type1 dendritic cell (cDC1)-dependent priming of CD8⁺T-cells in td-LNs. EF-PC accumulation reduced cDC1 activation and suppressed CCR7 expression, and impaired their migration into T-cell zones, resulting in failure in generating sufficient TCF1+ stem-like memory CD8+ T cells, a population required for sustained anti-tumour immunity. In vivo depletion of EF-PCs restored cDC1 activation and CCR7-dependent trafficking and positional licensing, expanded the stem-like central-memory CD8⁺ T-cell reservoir, increased infiltration of intratumoral CD8⁺ T-cell adopting an effector-memory phenotype, and ultimately reduced tumour growth.
Analysis of independent TNBC patient cohorts revealed that elevated EF-PC burden stratified patients with poorer prognosis and increased metastatic risk, specifically within immune-cold tumours. The EF-PC transcriptional signature aligned with previously described MT1X-high PC state linked to poor prognosis and resistance to ICB across multiple cancer types. Together, these findings position EF-PCs as a potential targetable checkpoint upstream of PD-1/ CTLA-4 in td-LNs and a therapeutic target for immune-cold TNBC and other cancers.
Limitations
Although the study demonstrates a clear immunosuppressive role for EF-PCs, the molecular mechanisms of EF-PC- mediated suppression cDC1 activation remain unresolved, including the ligand-receptor interactions or soluble mediators that may be involved.
Additionally, reliance on a single immune-cold TNBC murine model (4T1.2) may limit the generalisability of the findings across other tumour types and immune contexts. Human in vitro systems validation is also absent, thus a direct suppressive interaction between EF- PCs and cDC1s has yet to be confirmed in humans. Additionally, while the authors propose that plasma cell-targeting therapies could be used in immune-cold PC-high tumours unlikely to benefit from ICB alone, the potential risks associated with PC depletion, including impaired humoral immunity and increased susceptibility to infection, were not discussed. Identifying the precise molecular mechanism of EF-PC -mediated cDC1 suppression in the future would be valuable, as it could facilitate selective targeting without compromising protective antibody responses.
Significance/Novelty
This work highlights td-LNs, rather than the tumour microenvironment alone, as central sites of immune regulation in cancer, with direct implications for where and when therapeutic interventions should be applied. The authors identify EF-PCs as antibody-independent suppressors of the cDC1→CD8⁺ T-cell priming axis, introducing a new perspective on how immune-cold tumour escape effective immune surveillance.
The data also suggest that EF-PCs represent an immunoregulatory checkpoint upstream of conventional PD-1/CTLA-4, raising the possibility that therapeutic targeting of EF-DCs could enhance the efficacy of immunotherapy in poorly infiltrated tumours. More broadly, the study may have implications for cancer vaccination strategies that depend on effective cDC1 priming and expansion of the pool of progenitor stem-like CD8⁺ T-cells.
Credit
Reviewed by Yanshu Cai as part of a cross-institutional journal club between the Icahn School of Medicine at Mount Sinai, the University of Texas MD Anderson Cancer Center, the University of Oxford, the Karolinska Institute and the University of Toronto.
The author declares no conflict of interests in relation to their involvement in the review.