Agonistic anti-CD40 antibody treatment converts resident regulatory T cells into activated type 1 effectors within the tumor microenvironment

Vivien I Maltez; Charu Arora; Kyle P Gribbin; Breanna Caruso; Margaret E Haerr; Rina Sor; Qiaoshi Lian; Katie E Blise; Shamilene Sivagnanam; Rosalie C Sears; Lisa M Coussens; Robert H Vonderheide; Ronald N Germain; Katelyn T Byrne

doi:10.1016/j.immuni.2026.03.011

Agonistic anti-CD40 antibody treatment converts resident regulatory T cells into activated type 1 effectors within the tumor microenvironment

Immunity. 2026 Apr 2:S1074-7613(26)00122-6. doi: 10.1016/j.immuni.2026.03.011. Online ahead of print.

Authors

Affiliations

¹ Postdoctoral Research Associate Training (PRAT) Program Fellow, NIGMS, NIH, Bethesda, MD, USA; Lymphocyte Biology Section, Laboratory of Immune System Biology, NIAID, NIH, Bethesda, MD, USA.
² Abramson Cancer Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
³ Department of Cell, Developmental and Cancer Biology, Oregon Health and Science University, Portland, OR, USA.
⁴ Department of Cell, Developmental and Cancer Biology, Oregon Health and Science University, Portland, OR, USA; Graduate Program in Biomedical Sciences, Oregon Health and Science University, Portland, OR, USA.
⁵ Lymphocyte Biology Section, Laboratory of Immune System Biology, NIAID, NIH, Bethesda, MD, USA.
⁶ Department of Biomedical Engineering, Oregon Health and Science University, Portland, OR, USA; The Knight Cancer Institute, Oregon Health and Science University, Portland, OR, USA.
⁷ Department of Cell, Developmental and Cancer Biology, Oregon Health and Science University, Portland, OR, USA; The Knight Cancer Institute, Oregon Health and Science University, Portland, OR, USA.
⁸ The Knight Cancer Institute, Oregon Health and Science University, Portland, OR, USA; Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, OR, USA; Brenden-Colson Center for Pancreatic Care, Oregon Health and Science University, Portland, OR, USA.
⁹ Abramson Cancer Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Parker Institute for Cancer Immunotherapy, University of Pennsylvania, Philadelphia, PA, USA.
¹⁰ Lymphocyte Biology Section, Laboratory of Immune System Biology, NIAID, NIH, Bethesda, MD, USA; Center for Advanced Tissue Imaging (CAT-I), NIAID and NCI, NIH, Bethesda, MD, USA. Electronic address: rgermain@niaid.nih.gov.
¹¹ Department of Cell, Developmental and Cancer Biology, Oregon Health and Science University, Portland, OR, USA; The Knight Cancer Institute, Oregon Health and Science University, Portland, OR, USA; Brenden-Colson Center for Pancreatic Care, Oregon Health and Science University, Portland, OR, USA; Parker Institute for Cancer Immunotherapy, University of Pennsylvania, Philadelphia, PA, USA. Electronic address: byrneka@ohsu.edu.

PMID: 41932343
DOI: 10.1016/j.immuni.2026.03.011

Abstract

In pancreatic ductal adenocarcinoma (PDAC), agonistic anti-CD40 (αCD40) reduces frequencies of intratumoral regulatory T (Treg) cells despite a lack of CD40 expression on Treg cells. Here, we leveraged spatiotemporal imaging and lineage tracing approaches to examine intratumoral Treg cell fate in a mouse model of PDAC, where immune checkpoint blockade (ICB) (αPD-1 + αCTLA-4) combined with αCD40 controls tumor growth. Intratumoral Foxp3⁺ Treg cell numbers collapsed upon treatment, dependent on CD40-activated dendritic cells (DCs) and induction of interleukin (IL)-12 and interferon (IFN)-γ. This reduction corresponded with cellular alterations; Treg cells acquired an "ExTreg" phenotype characterized by loss of Foxp3 expression and acquisition of T helper 1 (Th1)-like features (Tbet⁺IFN-γ⁺). αCD40 promoted a spatially reorganized tumor microenvironment (TME), with Cxcr3⁺ Treg and ExTreg cells localized to the tumor periphery with Cxcl9-expressing DCs. Through in situ analyses of T cell receptor (TCR) signaling, we found that ExTreg cells had the highest antigen-driven activation among tumor-infiltrating T cells. Reprogramming of intratumoral Treg cells into Th1-like effectors reveals plasticity and an anti-tumor capacity of these cells.

Keywords: CD40 agonist; interferon-γ; regulatory T cell; reprogramming; tumor microenvironment.