A New Approach to Type 1 Diabetes: Using Transplanted Islets to Retrain the Immune System

Researchers at a single center tested a novel idea: what if a small islet transplant could be used not to provide insulin, but to retrain the immune system? In Type 1 diabetes, the immune system mistakenly attacks insulin-producing beta cells. Most transplant approaches try to replace lost insulin production. This study took a different path, intentionally transplanting too few islets to do that job, but hoping the transplant itself would trigger immune 'education'—a reset that stops the attack on beta cells.

Six patients with recent-onset Type 1 diabetes received minimal amounts of donor islets (an average of 3,452 insulin-equivalent units per kilogram of body weight). The transplant was paired with short-term immune medications: ATG (a lymphocyte-depleting drug), temporary mTOR inhibition, and G-CSF (which promotes certain immune cell growth). The idea was that this combination would create an environment where the immune system could 'learn' tolerance.

At 12 months, the results were encouraging. All six participants showed preserved C-peptide levels—a marker of the body's remaining insulin production—at 91-100% of their baseline measurements. This means the transplant and immune treatment did not further damage the remaining beta cells, and may have protected them. All six also achieved what researchers call 'partial clinical remission,' meaning better blood sugar control with reduced insulin needs (IDAA1c score of 9 or lower).

The study protocol was safe and well-tolerated, with no serious adverse events reported. These early results suggested the approach was worth examining further.

The picture became more complicated in the longer term. By five years, median C-peptide levels had declined to 44-56% of baseline. However, four of the six patients retained measurable beta-cell function, with two maintaining stable secretion and two retaining roughly half of their initial production. This suggests the transplant and immune treatment had a durable—though diminishing—effect in some participants.

The decline over time highlights a key challenge: even with immune-modulating drugs, the underlying autoimmune process may eventually resurface. Whether additional interventions might sustain the benefit longer is an open question.

Detailed immune monitoring revealed a structured pattern of change. Early on, the drugs caused lymphodepletion—a temporary reduction in immune cells. This was followed by expansion of memory and regulatory T cells, which normally help control immune responses. The researchers also observed transient increases in IL-2 and IL-10, immune-signaling molecules associated with tolerance-promoting responses.

These findings suggest that the transplant combined with the immune drugs may have genuinely reset immune tolerance, at least in the early phase. However, this study was too small and the follow-up data too preliminary to draw firm conclusions about whether this immune 'reprogramming' is a reproducible mechanism or how to optimize it.

This pilot study demonstrates that the concept of using a minimal islet transplant as a platform for immune education is feasible and safe in people with recent-onset Type 1 diabetes. The one-year results are noteworthy: sustained C-peptide preservation and improved metabolic control in all participants.

However, this is a very early-stage study with only six people and limited long-term follow-up data. To know whether this approach could help patients more broadly, researchers would need larger trials, longer follow-up, and a better understanding of who is most likely to benefit and how to extend the effects over time. The decline in function by year five also underscores that durable immune tolerance—the ultimate goal—has not yet been achieved.

This work represents one of several investigational strategies aimed at preserving or restoring beta-cell function in Type 1 diabetes. Alongside other immunotherapies and regenerative approaches, it offers a window into how science is exploring new ways to address the disease at an immunological level.

Source: EClinicalMedicine. Evidence type: PubMed indexed literature. Type1Cure is an information and intelligence hub, not a medical advice service. This article summarizes published research and does not provide diagnosis, treatment, or personal medical guidance. Always talk to your own care team before changing anything about your Type 1 diabetes management.