Tumor-specific CD4 T cells cooperate with myeloid cells to remodel the pancreatic tumor microenvironment and enable effective immunotherapy

Cruz-Hinojoza, E.; Schmiechen, Z. C.; Bonner, S. M.; Burrack, A. L.; Ellefson, M. A.; Gaire, A.; Pandey, R.; Appiah, S.; Shen, S. S.; Dileepan, T.; Stromnes, I. M.

doi:10.64898/2026.07.28.741325

bioRxiv · 10.64898/2026.07.28.741325

Tumor-specific CD4 T cells cooperate with myeloid cells to remodel the pancreatic tumor microenvironment and enable effective immunotherapy

Cruz-Hinojoza, E.·Schmiechen, Z. C.·Bonner, S. M.·Burrack, A. L.·Ellefson, M. A.·Gaire, A.·Pandey, R.·Appiah, S.·Shen, S. S.·Dileepan, T.·Stromnes, I. M.

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Abstract

We interrogate antigen-specific CD4 T cells during immunotherapy in pancreatic ductal adenocarcinoma. Vaccination with MHC-II-restricted tumor epitopes impart superior protection compared to an immunodominant MHC-I epitope, prompting development of MHC-II affinity-enhanced tetramers to track tumor-specific CD4 T cells. As tumors progress, tumor-specific CD4 T cells decline, and remaining cells acquire features of regulation. Agonistic anti-CD40 increases Th1 cell clonal expansion and transiently decreases Tregs. Anti-PD-L1 promotes Tfh clonal expansion in draining lymph nodes and tumor while preventing Treg rebound after anti-CD40. Treatment with anti-CD40 promotes intratumoral Stat1+ macrophages, tertiary lymphoid structures (TLS), and immune triads. MHC-II on myeloid cells but not B cells is required for immunotherapy-induced TLS formation and antitumor effects. IL-15 complex enhances immunotherapy-induced Th1 effectors without promoting Tregs. Human immunotherapy transcriptomics shows conserved Th1 programming and Treg destabilization as a feature of response. Thus, tumor-specific CD4 T cells are central mediators of effective immunotherapy in solid tumors.

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Cruz-Hinojoza, E., Schmiechen, Z. C., Bonner, S. M., Burrack, A. L., Ellefson, M. A., Gaire, A., Pandey, R., Appiah, S., Shen, S. S., Dileepan, T., Stromnes, I. M.. 2026-08-01. Tumor-specific CD4 T cells cooperate with myeloid cells to remodel the pancreatic tumor microenvironment and enable effective immunotherapy. https://doi.org/10.64898/2026.07.28.741325

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