Research ArticleOncology Open Access | 10.1172/jci.insight.188843

Nicole L. Huang,1 Jessica G. Ortega,2 Kyleigh Kimbrell,1 Joah Lee,1 Lauren N. Scott,3 Esther M. Peluso,4 Sarah J. Wang,1 Ellie Y. Kao,5 Kristy Kim,1 Jarod Olay,6 Jaden N. Nguyen,6 Zoe Quandt,7 Trevor E. Angell,8 Maureen A. Su,6,9 and Melissa G. Lechner1

1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

Find articles by Angell, T. in: PubMed | Google Scholar |

1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

Find articles by Su, M. in: PubMed | Google Scholar |

1Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

2UCSF Medical School, San Francisco, California, USA.

3University of Kansas Medical School, Kansas City, Kansas, USA.

4UCLA/California Institute of Technology Medical Scientist Training Program, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

5California State Polytechnic University, Pomona, California, USA.

6Department of Microbiology, Immunology, and Molecular Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA.

7Division of Endocrinology and Metabolism, UCSF Medical School, San Francisco, California, USA.

8Division of Endocrinology and Diabetes, University of Southern California Keck School of Medicine, Los Angeles, California, USA.

9Division of Pediatric Endocrinology, UCLA David Geffen School of Medicine; Los Angeles, California, USA.

Address correspondence to: Melissa G. Lechner, Division of Endocrinology, Diabetes, and Metabolism, UCLA David Geffen School of Medicine, 10833 Le Conte Ave., CHS 32-176, Los Angeles, California, 90095, USA. Email: MLechner@mednet.ucla.edu.

Authorship note: NLH and JGO contributed equally to this work.

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Authorship note: NLH and JGO contributed equally to this work.

Published July 8, 2025 - More info

Published in Volume 10, Issue 13 on July 8, 2025
JCI Insight. 2025;10(13):e188843. https://doi.org/10.1172/jci.insight.188843.
© 2025 Huang et al. This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Published July 8, 2025 - Version history
Received: November 7, 2024; Accepted: May 13, 2025 View PDF Abstract

Immune checkpoint inhibitors (ICI) have revolutionized cancer therapy, but their use is limited by the development of autoimmunity in healthy tissues as a side effect of treatment. Such immune-related adverse events (IrAE) contribute to hospitalizations, cancer treatment interruption, and even premature death. ICI-induced autoimmune diabetes mellitus (ICI-T1DM) is a life-threatening IrAE that presents with rapid pancreatic β-islet cell destruction leading to hyperglycemia and life-long insulin dependence. While prior reports have focused on CD8+ T cells, the role for CD4+ T cells in ICI-T1DM is less understood. We identify expansion of CD4+ T follicular helper (Tfh) cells expressing IL-21 and IFN-γ as a hallmark of ICI-T1DM. Furthermore, we show that both IL-21 and IFN-γ are critical cytokines for autoimmune attack in ICI-T1DM. Because IL-21 and IFN-γ both signal through JAK/STAT pathways, we reasoned that JAK inhibitors (JAKi) may protect against ICI-T1DM. Indeed, JAKi provide robust in vivo protection against ICI-T1DM in a mouse model that is associated with decreased islet-infiltrating Tfh cells. Moreover, JAKi therapy impaired Tfh cell differentiation in patients with ICI-T1DM. These studies highlight CD4+ Tfh cells as underrecognized but critical mediators of ICI-T1DM that may be targeted with JAKi to prevent this grave IrAE.

Graphical Abstract Introduction

Immune checkpoint inhibitor (ICI) therapies have significantly improved outcomes for patients with many types of advanced cancers. However, their use is limited by the development of autoimmune toxicities in healthy tissues in nearly two-thirds of patients (1–3). ICI-induced autoimmune diabetes mellitus (ICI-T1DM) is a rare but life-threatening immune-related adverse event (IrAE) that occurs in 1%–2% of patients treated with ICI (4). ICI-T1DM presents as a rapidly progressive autoimmune destruction of pancreas β-islet cells, accompanied by hyperglycemia and often ketoacidosis (4–6). Patients with ICI-T1DM have permanent pancreatic endocrine insufficiency and require life-long insulin replacement therapy. In patients receiving ICI therapy for advanced malignancies, this additional comorbidity can add another debilitating and overwhelming layer of complexity to their care. On the other hand, in the growing number of patients who receive ICI therapy for early stage or curable disease, ICI-T1DM represents a permanent sequela of treatment that can negatively affect quality of life long after cancer resolution.

Currently, no therapies exist to prevent endocrine IrAEs, including ICI-T1DM (4, 5, 7–9). Understanding immune mechanisms that drive autoimmunity may identify therapeutic targets to reduce IrAEs. We recently identified IL-21+ T follicular helper (Tfh) cells as critical mediators of ICI-thyroiditis (10), another common endocrine IrAE seen in 15%–25% of patients treated for ICI. Like ICI-T1DM, ICI-thyroiditis presents as brisk autoimmune destruction of thyroid gland cells and loss of thyroid function over a period of weeks (9, 11). We found that thyrotoxic IFN-γ+CD8+ T cells in the thyroid were driven by IL-21 from CD4+ Tfh cells and inhibition of IL-21 prevented ICI-thyroiditis (10). Whether Tfh cells contribute to the development of ICI-T1DM and may be therapeutically targeted to reduce pancreas autoimmunity during ICI therapy has not yet been explored.

In addition to developing mechanism-based therapies for IrAEs, a practical consideration is the urgent need for near-term strategies to reduce autoimmunity in the many patients currently receiving ICI therapy. As clinical indications for ICI therapy expand (12), the number of patients with IrAEs will surge — as will the need for therapies to halt severe or life-threatening autoimmune toxicities like ICI-T1DM. Janus kinase inhibitors (JAKi) are a class of orally bioavailable medications now widely used to treat spontaneous autoimmune diseases like alopecia, psoriasis, and arthritis (13–15). These agents block JAK signaling, which is required for many T cell cytokine responses (13). Indeed, Waibel et al. (16) reported preservation of β-islet cell function and decreased insulin requirements in individuals with spontaneous T1DM in a phase 2 trial of JAKi baricitinib. However, the potential of JAKi to halt the rapid and often fulminant autoimmune responses seen in IrAEs has only been explored recently. JAK1/2 inhibitor ruxolitinib notably improved survival from 3.4% to 60% in a cohort of patients with steroid refractory ICI-myocarditis, another rare but deadly IrAE, when given in combination with CTLA-4 agonist abatacept (17). Based upon their promise in spontaneous autoimmune diseases and ICI-myocarditis, we hypothesized that JAKi could be utilized to prevent endocrine IrAEs.

In this study, we identify multifunctional CD4+ Tfh cells expressing IL-21 and IFN-γ as antigen-specific mediators of autoimmune tissue injury in ICI-T1DM. Furthermore, we show that both IL-21 and IFN-γ are critical cytokines in autoimmune attack during ICI-T1DM and that inhibition of these cytokine pathways by JAKi therapy can prevent ICI-T1DM. Moreover, we show that JAKi treatment decreases islet-infiltrating Tfh cells in a mouse model of IrAEs and Tfh cell differentiation in patients with ICI-T1DM. These studies highlight CD4+ Tfh cells as underrecognized but critical mediators of ICI-T1DM that may be targeted with JAKi to prevent this life-threatening endocrine IrAE.

Results

Individuals with ICI-T1DM have increased Tfh cell responses. Tfh cells contribute to multiple spontaneous autoimmune diseases, including T1DM (18, 19), where they can signal to B cells in germinal centers and promote pathogenicity of CD8+ T cells (10, 18–21). Expansion of Tfh cells has recently been linked to the development of IrAEs in patients treated for ICI. Herati et al. (22) reported an increase in circulating Tfh cells after influenza vaccination in anti–PD-1–treated patients who went on to develop IrAEs. Furthermore, in individuals with ICI-thyroiditis, IL-21+ CD4+ Tfh cells are key drivers of thyroid autoimmune attack (10). Therefore, we hypothesized that Tfh cells may also contribute to the development of ICI-T1DM.

To test this idea, we evaluated Tfh cells (CD4+ICOS+PD-1hiCXCR5+) in peripheral blood specimens from patients with ICI-T1DM versus patients who received ICI therapy but did not develop IrAEs. Because prior work showed that Tfh cell response, but not baseline levels of circulating Tfh cells, was predictive of IrAEs, we compared the magnitude of Tfh cell expansion between groups after Tfh skewing ex vivo (23) (Figure 1A). Indeed, patients with ICI-T1DM had a more robust Tfh cell response than those without IrAEs, with increased CD4+ICOS+PD-1hiCXCR5+ cells compared with controls without autoimmunity (Figure 1B; P < 0.05). These data suggest that individuals with ICI-T1DM have increased CD4+ Tfh cell responses compared with individuals who do not develop IrAEs.

Figure 1

Increased CD4+ Tfh cell response in individuals with ICI-T1DM and a mouse model of IrAEs. (A) Representative flow cytometry of PBMC from ICI-treated patients at baseline and after ex vivo culture under Tfh-skewing conditions (23). (B) Fold change in Tfh cell frequency for individuals with ICI-T1DM versus ICI-treated individuals with no irAEs. Each pair represents 1 individual. (C) DM incidence in NOD mice treated with anti–PD-1 (8 males [M]/8 females [F]) or isotype (Iso) (6M/7F). (D) DM incidence in anti–PD-1 treated NOD mice with a depleting anti-CD4 antibody (5M/5F) or isotype (Mock) (2M/2F). (E) Representative flow cytometry for islet-infiltrating Tfh cells. (F) Quantification of Tfh cells (CD4+ICOS+PD-1hiCXCR5+) within islets of anti–PD-1–treated (n = 16) versus Iso-treated (n = 8) mice. (G) Quantification of Bcl6+Tbet– and Bcl6+Tbet+ subsets within CD4+ICOS+PD-1hiCXCR5+ cells in the islets of anti–PD-1–treated (n = 6) versus Iso-treated (n = 5) mice. (H) Representative flow cytometry and quantification of islet-infiltrating IL-21– and IFN-γ–producing Tfh cells in Iso-treated (n = 7) and anti–PD-1–treated (n = 13) mice. (I) Quantification of IL-21+IFN-γ– and IL-21+IFN-γ+ subsets within CD4+ ICOS+PD-1hiCXCR5+ cells in the islets of anti–PD-1–treated (n = 19) versus Iso-treated (n = 8–9) mice. (J) Quantification of BDC2.5-mimotope tetramer+ Tfh cells within the islets of Iso-treated (n = 6) versus anti–PD-1–treated (n = 5) mice. (K) Comparison of islet-infiltrating IL-21+IFN-γ+tetramer+CD4+ Tfh cells between anti–PD-1–treated (n = 4) and Iso-treated (n = 5) mice. Each point represents data from 1 animal, and data are presented as mean ± SD. Comparisons by 2-way ANOVA for paired samples with subsequent pairwise comparisons (B), log-rank test (C and D), Welch’s t test (G), Brown-Forsythe and Welch ANOVA (I), or Mann-Whitney U test (F, J, and K); *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.

Antigen-specific IL-21+IFN-γ+CD4+ Tfh cells are increased in the pancreatic islets of mice with ICI-T1DM. To better understand the role of Tfh cells in the immunopathogenesis of ICI-T1DM in vivo, we then used a mouse model of IrAEs. Previously, we reported the development of multiorgan immune infiltrates in autoimmunity-prone nonobese diabetic (NOD) mice following ICI treatment, including thyroiditis, colitis, and accelerated DM (10, 24). As expected, male and female NOD mice (7–9 weeks of age) treated with continued cycles of anti–programmed death 1 (anti–PD-1) antibody (10 mg/kg/dose, twice weekly), developed ICI-T1DM at a median of 10 days, while isotype-treated controls remained healthy after 4 weeks (Figure 1C; P < 0.0001).

T cells play a key role in the development of IrAEs in multiple tissues (10, 25–28), including the pancreas (4, 29–31). As expected, NOD mice with genetic deletion of TCRα, which leads to an absence of mature CD4+ and CD8+ T cells, were completely protected from ICI-T1DM (Supplemental Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.188843DS1). Prior studies have demonstrated the importance of IFN-γ–producing CD8+ T cells in mouse models of ICI-T1DM (29–31). On the other hand, the role of CD4+ T cells has been less explored but is important in other IrAEs (10, 24, 32–34). Additionally, because CD4+ T cell responses may not be as central to ICI antitumor efficacy, they might be therapeutic targets to reduce IrAEs in patients with cancer while preserving efficacy (24, 32, 35).

Antibody depletion of CD4+ T cells in ICI-treated WT NOD mice significantly delayed the onset of autoimmune diabetes (Figure 1D and Supplemental Figure 1B), suggesting a CD4+ T cell contribution to ICI-T1DM disease progression. We then compared the frequency of CD4+ Tfh cells within pancreatic islets of NOD mice after 3 weeks of anti–PD-1 or isotype control therapy (Figure 1E). Indeed, anti–PD-1–treated mice had increased islet-infiltrating Tfh cells (CD4+ICOS+PD-1hiCXCR5+) compared with isotype controls (Figure 1F,]; P < 0.01) — a trend toward increased Tfh cells was also found in pLN — but this difference was not statistically significant (Supplemental Figure 1C). Within this putative ICOS+PD-1hiCXCR5+CD4+ Tfh cell population, we identified both Bcl6+Tbet– Tfh and Bcl6+Tbet+ Tfh-like subsets that were increased within the pancreatic islets of anti–PD-1–treated mice (Figure 1G; P < 0.05 for both). We next evaluated IL-21 and IFN-γ cytokine production by islet-infiltrating Tfh cells by flow cytometry (Figure 1H). Dual producing IL-21+IFN-γ+ Tfh cells were increased within the islets of anti–PD-1 treated mice (Figure 1I, P < 0.01), with a nonsignificant trend within the islets for increased IL-21+IFN-γ– Tfh cells (Figure 1I, P = ns). Such multifunctional IL-21+IFN-γ+ Tfh CD4+ cells have previously been described as mediators of immune response in spontaneous autoimmune diseases (e.g., lupus and peripheral neuropathy) and viral infections (36–39). In summary, anti–PD-1 treatment and development of ICI-T1DM is associated with islet infiltration by Bcl6+Tbet– Tfh and Bcl6+Tbet+ Tfh-like cells expressing IL-21 and IFN-γ.

In spontaneous T1DM, autoimmune Tfh cells classically reside within pancreatic lymph nodes (pLN) and can traffic into inflamed islets (40, 41). While we did not observe a significant increase in ICOS+ PD-1hiCXCR5+CD4+ Tfh cells within pLN following anti–PD-1 therapy (Supplemental Figure 1C), ICI treatment increased Tfh cell expression of chemokine receptors associated with trafficking to inflamed pancreatic islets, including CXCR6 (29, 30, 41) (Supplemental Figure 1D). Indeed, islet-infiltrating IL-21+IFN-γ+ Tfh cells expressed CXCR6+ that was increased with anti–PD-1 therapy (Supplemental Figure 1E). These data suggest that pLN Tfh cells may upregulate CXCR6 and migrate to the islet in response to ICI treatment.

We then wondered whether islet-infiltrating IL-21+IFN-γ+ Tfh cells were autoantigen specific or responding as bystanders to the inflamed islet. Fife and colleagues previously established a pathogenic role for BDC2.5-mimotope CD4+ T cells in NOD mice with accelerated autoimmune DM due to loss of PD-1 (42). Therefore, we used an MHC class II BDC2.5 tetramer to quantify autoantigen-specific CD4+ T cells in our mouse model. Twenty-seven percent of islet-infiltrating BDC2.5-mimotope tetramer+CD4+ T cells (hereafter referred to as tetramer+) had a surface phenotype consistent with Tfh cells (ICOS+PD-1hiCXCR5+) by flow cytometry (Supplemental Figure 2, A and B), expressed canonical Tfh transcription factor Bcl6 (Supplemental Figure 2, C and D), and produced cytokines IL-21 and IFN-γ (Supplemental Figure 2, E and F). Furthermore, anti–PD-1–treated mice had more tetramer+ CD4+ Tfh cells in pancreatic islets compared with isotype-treated controls (Figure 1J; P < 0.01), and these cells showed high dual expression of IL-21 and IFN-γ (Figure 1K; P < 0.05). Taken together, these data support a role for antigen-specific, polyfunctional IL-21+IFN-γ+CD4+ Tfh cells in the autoimmune attack on pancreas β-islet cells during ICI therapy.

IL-21 and IFN-γ are important cytokine mediators of ICI-T1DM. We hypothesized that inhibition of Tfh cytokines, specifically IL-21 and IFN-γ (Figure 2A), could attenuate autoimmune attack on the pancreas during anti–PD-1 therapy. IL-21 is a pleiotropic cytokine that can promote effector functions in CD8+ T cells (10, 20, 21) and B cell antibody production (43). In humans and mice, CD4+ Tfh cells are the primary source of IL-21 (18, 44). Indeed, NOD mice with genetic deletion of IL-21 signaling (NOD.Il21r–/–, IL-21R KO) were protected from the development of ICI-T1DM during ICI treatment (Figure 2B; P < 0.0001 for anti–PD-1 therapy in WT versus IL-21R–KO mice). It is recognized that IL-21 is required for the development of spontaneous T1DM in NOD mice (40, 45), and these data establish a role for IL-21 in ICI-T1DM as well.

Figure 2

IL-21 and IFN-γ are key cytokine mediators of ICI-T1DM. (A) Schematic of cytokine production by Tfh cells. (B) Incidence curve for ICI-T1DM in anti–PD-1 treated NOD WT and NOD.Il21r–/– (IL-21R KO) mice. WT, Iso (6 males, 7 females); IL-21R–KO, Iso (11 males); IL-21R–KO, anti–PD-1 (8 males, 2 females). (C) Incidence curve for ICI-T1DM in ICI-treated NOD WT and NOD.IFN-γ–/– (IFN-γ–KO) mice during anti–PD-1 treatment. WT, Iso (6 males, 7 females); IFN-γ–KO, Iso (6 males, 3 females); IFN-γ–KO, anti–PD-1 (6 males, 7 females), WT, anti–PD-1 (3 males, 4 females). (D) Representative H&E-stained pancreas histology sections of Iso- or anti–PD-1–treated WT, IL-21R–KO, or IFN-γ–KO mice (original magnification, 100×). Arrow indicates an islet of Langerhans. (E) Insulitis index determined by histologic analyses of pancreas islet histology across indicated treatment conditions. WT, Iso (5 males, 10 females); WT, anti–PD-1 (6 males, 10 females); IL-21R–KO, anti–PD-1 (4 males, 1 female); IFN-γ–KO, anti–PD-1 (5 males, 5 females). (F) Quantification of CD4+ T, CD8+ T, and B cells from anti–PD-1–treated WT (2 males, 2 females), IL-21R–KO (2 males, 1 female), and IFN-γ–KO (5 males, 4 females) mice or Iso WT (1 male, 3 females), via multi-immunofluorescence staining. Comparisons by log-rank test (B and C), Fisher’s exact test (E), or Brown-Forsythe ANOVA with Welch’s pairwise comparison test (F). **P < 0.01, ***P < 0.001, ****P < 0.0001.

IFN-γ is expressed more broadly, including by both CD4+ and CD8+ T cells in ICI-T1DM (29–31). NOD mice with genetic deletion of the IFN-γ gene (NOD.IFN-γ–/–, IFN-γ KO) showed significantly delayed onset of ICI-T1DM (