How much low-dose IL-2 boosts protective T cells in type 1 diabetes?
A single very low dose of the immune signalling drug IL-2 raised regulatory T cells in a dose-dependent way in adults with type 1 diabetes, and doses that gave 10% and 20% increases were identified and well tolerated.
Source
Regulatory T Cell Responses in Participants with Type 1 Diabetes after a Single Dose of Interleukin-2: A Non-Randomised, Open Label, Adaptive Dose-Finding Trial
Study at a glance
- Design
- Human experiment — Single-centre, non-randomised, open-label adaptive dose-finding trial: a learning phase of ten participants on ascending doses, then 30 participants whose doses were chosen by interim model fits, each receiving one subcutaneous dose of aldesleukin and followed for 60 days.
- N
- N=40 · 40 participants received a single dose (safety and analysis populations); 39 formed the evaluable population after one withdrew with norovirus; subgroup assays had fewer participants because of missing data.
- Population
- Adults aged 18-50 with type 1 diabetes diagnosed less than two years earlier and at least one diabetes autoantibody, recruited to Cambridge, UK
- Outcome
- Maximum percentage increase in regulatory T cells (as a share of CD4+ T cells) within 7 days after dosing; secondary immune, safety and metabolic measures
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
Forty adults recently diagnosed with type 1 diabetes each received one injection of aldesleukin (a manufactured form of the immune signal IL-2) at doses far below those used in cancer treatment. The first ten participants received doses in ascending order; for the next 30, statisticians refitted dose-response models after each person and a committee chose the next dose to pin down the target doses efficiently. Blood was sampled at 90 minutes, daily for four days and then intermittently to day 60, measuring regulatory T cells, effector T cells, natural killer cells, IL-2 levels and safety markers.
What they found
Regulatory T cells rose with dose after a brief early dip, peaking around day 3; the estimated doses for a 10% and a 20% increase were 0.101 and 0.497 million IU/m2. There were no serious adverse events; most people had a mild injection-site rash and one had a self-limiting norovirus infection. Even the lowest doses briefly activated some effector T cells and natural killer cells, and the IL-2 receptor subunit CD122 on regulatory T cells dropped sharply, making them temporarily less sensitive to further IL-2. Higher doses caused a short dip in lymphocytes, a rise in eosinophils and increases in the inflammatory marker CRP.
The limits
What it doesn't show
This was a mechanistic trial of a single dose, not a test of whether IL-2 preserves insulin production or improves diabetes; the small apparent improvements in glucose and HbA1c may reflect extra specialist care. There was no placebo group and no randomisation, and the sample was small with only four people at the highest doses. Only adults and only blood were studied, so effects in children or in the pancreas itself are unknown, and repeated dosing may behave differently because of receptor desensitisation.
Key terms
- Regulatory T cell (Treg)
- A type of CD4+ T cell that suppresses other immune cells and helps prevent the immune system from attacking the body's own tissues.
- Effector T cell (Teff)
- A T cell that carries out immune attacks; in type 1 diabetes autoreactive effector T cells destroy insulin-producing beta cells.
- Aldesleukin
- A recombinant (lab-made) form of the cytokine IL-2, licensed at high doses for some cancers.
- Adaptive dose-finding design
- A trial design in which accumulating results are analysed during the study to choose the doses given to later participants.
- Desensitisation
- A temporary drop in a cell's responsiveness to a signal, here caused by loss of the CD122 IL-2 receptor subunit after exposure to IL-2.
- C-peptide
- A fragment released alongside insulin; its level in the blood is used to measure a person's own remaining insulin production.
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What kind of trial was DILT1D?
Common questions
Why would boosting regulatory T cells help type 1 diabetes?
Type 1 diabetes is caused by T cells destroying the insulin-producing cells of the pancreas. Genetic studies link weak IL-2 signalling and poorer Treg function to the disease, so raising Treg activity might restrain the autoimmune attack and preserve remaining insulin production.
Why not simply give the high doses used in cancer?
High-dose IL-2 strongly activates effector T cells and natural killer cells, which is the goal in cancer but would risk worsening autoimmunity. Low doses exploit the fact that Tregs are more sensitive to IL-2, though this study showed the selectivity is not complete.
What should the next trial test?
The authors propose testing repeated doses between the two identified levels at intervals of more than two days to reach a steady rise in Tregs, followed by a phase 2 efficacy trial measuring insulin preservation.
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