# Notch Signaling in Alloimmunity

> **NIH NIH R01** · UNIVERSITY OF PENNSYLVANIA · 2021 · $406,145

## Abstract

ABSTRACT
Allogeneic T cell responses against foreign host antigens mediate graft-versus-host disease, the most
serious complication of allogeneic hematopoietic cell transplantation (allo-HCT). During the course of this
proposal we defined a critical role for Notch signaling in the regulation of pathogenic alloreactive T cells
that mediate graft-versus-host disease (GVHD) in multiple mouse models of allo-HCT. Notch inhibition in
donor T cells led to long-term protection from GVHD morbidity and mortality. Using monoclonal antibodies,
we identified a critical role for Notch1/2 receptors in T cells and Delta-like1/4 (Dll1/4) Notch ligands in the
host, with dominant effects of Notch1 and Dll4. Dll1/4 blockade with a short course of antibodies emerged
as the most promising strategy to target Notch signaling while avoiding systemic side effects of pan-Notch
inhibition. We recently uncovered several remarkable features of Notch regulation in T cell alloimmunity
that warrant further investigation. First, we identified specialized radioresistant stromal cells lineage-traced
with a Ccl19-Cre transgene as the critical source of Notch ligands in secondary lymphoid organs at the
onset of GVHD. These findings uncover a central role for fibroblastic stromal cell subsets in GVHD. Second,
short-term inhibition of Delta-like Notch ligands within days after allo-HCT was essential to confer long-
term protection from GVHD in multiple mouse models. Within this early time window, Notch induced unique
transcriptional effects during the activation of alloantigen-specific T cells that impacted selected aspects of
their differentiation. Third, we studied Notch ligand inhibition in a non-human primate allo-HCT model that
mimics human transplantation. A single dose of anti-DLL4 antibodies had marked single agent activity to
prevent GVHD, showing highly conserved effects of Notch signaling from mice to non-human primates. In
both models, we observed an increased ratio of regulatory to conventional T cells in the gut and striking
protection from intestinal GVHD, the most dangerous component of acute GVHD. We hypothesize that
alloantigen-specific T cells engage in early interactions with specialized subsets of fibroblastic stromal cells
expressing Delta-like Notch ligands, inducing a Notch-driven pathogenic and gut-homing program in T cells
that promotes GVHD. To explore this hypothesis, we will identify individual subsets of fibroblastic stromal
cells that present Dll1 and/or Dll4 Notch ligands to donor-derived T cells early after allo-HCT, map the
anatomical sites that support Notch activation in alloreactive T cells, and define the impact of immune-
mediate injury on the subsequent integrity of stromal networks in secondary lymphoid organs. In addition,
we will identify mechanisms that blunt the accumulation of Notch-deficient T cells in the gut, thus preventing
intestinal GVHD, and investigate the early transcriptional effects of Notch signaling in alloreactive T cells.
The...

## Key facts

- **NIH application ID:** 10146004
- **Project number:** 2R01AI091627-12
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** Ivan Maillard
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $406,145
- **Award type:** 2
- **Project period:** 2011-04-22 → 2026-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10146004

## Citation

> US National Institutes of Health, RePORTER application 10146004, Notch Signaling in Alloimmunity (2R01AI091627-12). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10146004. Licensed CC0.

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