# Thymic negative selection in human T1D immune systems

> **NIH NIH R21** · COLUMBIA UNIVERSITY HEALTH SCIENCES · 2020 · $198,073

## Abstract

In healthy individuals, central and peripheral immune tolerance mechanisms prevent autoimmune disease. One
or more of these mechanisms is disrupted in Type 1 diabetes (T1D) patients, resulting in autoimmune destruction
of insulin-producing pancreatic beta cells. In the NOD mouse model, defects in thymic negative selection have
been strongly implicated in disease development. Introduction of an insulin-reactive T-cell receptor (TCR)
derived from a T1D patient to peripheral T cells of humanized mice can initiate diabetes, consistent with the
notion that escape of autoreactive T-cells from negative selection can promote disease. On the other hand, beta
cell antigen-reactive T-cells have also been isolated from the blood of healthy control (HC) individuals, raising
the possibility that defective peripheral tolerance mechanisms may be most important in promoting T1D. Genetic
studies have identified over 60 risk variants for T1D, including associations with genes implicated in deletion of
developing autoreactive T cells during thymic negative selection. To date, however, there has been no method
available to model human patient-specific thymic selection, resulting in uncertainty about the role of defects in
this pathway in promoting human autoimmune diseases. We hypothesize that there are specific
hematopoietic stem cell (HSC)-intrinsic and thymus-intrinsic genetic variants in T1D individuals that lead
to the failure of negative selection of diabetogenic T-cell receptors (TCRs) in the thymus. We have
established a Personalized Immune (PI) mouse model that allows us to generate an adult human's immune
system de novo in immunodeficient NOD/LtSz-scid IL2R gamma null mice (NSG) mice receiving patient HSCs
and a partially HLA-matched fetal thymus graft. We have also demonstrated that adult patient HSCs can be
lentivirally transduced to express a TCR and subsequently used to reconstitute NSG mice or human thymus
tissue in thymic organ culture assays. We have demonstrated that a diabetogenic insulin B(9-23)/HLA-DQ8-
specific autoreactive TCR is normally deleted within the thymus of humanized mice constructed with HLA-DQ8+
thymic tissue and HSCs. With these data and with access to HSCs from T1D and HC donors and to thymi from
the network for Pancreatic Organ Donors with Diabetes (nPOD), we have demonstrated the feasibility of our
proposed study. We will use these innovative in vitro and in vivo models to assess whether or not there is a
defect in thymic negative selection in immune systems derived from T1D patients and determine whether such
defects are intrinsic to the patient HSCs or to T1D thymic tissue. We will associate such defects with genetic
risk variants and address hypotheses about the impact of specific variants that may impact negative selection in
an HSC- or thymic tissue-dependent manner. These studies will not only provide unprecedented information on
the role of defective negative selection in T1D pathogenesis and the genetic determinants of t...

## Key facts

- **NIH application ID:** 9961490
- **Project number:** 5R21AI146828-02
- **Recipient organization:** COLUMBIA UNIVERSITY HEALTH SCIENCES
- **Principal Investigator:** Megan Sykes
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $198,073
- **Award type:** 5
- **Project period:** 2019-06-20 → 2022-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9961490

## Citation

> US National Institutes of Health, RePORTER application 9961490, Thymic negative selection in human T1D immune systems (5R21AI146828-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9961490. Licensed CC0.

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