Northwestern Medicine researchers have identified the cellular mechanisms behind a novel nanoparticle therapy that could transform how doctors treat autoimmune diseases by retraining the immune system rather than simply suppressing it. In a study published in Science Advances, scientists discovered that biodegradable nanoparticles trigger a natural tolerance pathway in the body, leading to the creation of regulatory T-cells that prevent autoimmune attacks on healthy tissue .

What Happens When Your Immune System Attacks Itself?

Autoimmune diseases occur when the immune system, particularly a type of white blood cell called autoreactive T-cells, mistakenly targets and destroys healthy cells and tissues. Currently, nearly 100 known autoimmune diseases are treated with general immunosuppressive therapies that broadly dampen immune activation, migration, and function. However, these broad-spectrum approaches come with significant side effects because they weaken the entire immune system, leaving patients vulnerable to infections and other complications .

The new nanoparticle approach works differently. Instead of shutting down the immune system wholesale, it aims to "retrain" it by inhibiting the inflammatory T-cells driving autoimmunity while simultaneously inducing regulatory T-cells that actively prevent autoimmune responses. In a previous clinical trial, the gliadin-containing nanoparticle treatment blocked both intestinal changes and an increase in inflammatory T-cells in the blood following gluten challenge in patients with celiac disease .

How Do These Nanoparticles Actually Work Inside Your Body?

The research team used advanced techniques including traceable nanoparticles, single-cell RNA sequencing, and laboratory cell cultures to map exactly what happens when these nanoparticles enter the body. The discovery reveals an elegant biological mechanism that leverages the body's own natural tolerance pathways .

When injected, the nanoparticles are engulfed by myeloid cells, which are immune cells originating from bone marrow. These cells break down the nanoparticles through a process called phagocytosis. Crucially, this breakdown triggers a form of cell death called apoptosis, which releases oxidized DNA into the cellular environment. This oxidized DNA then activates the STING pathway, a natural immune signaling system that releases type-I interferons, which are cytokines known for driving inflammatory immune responses .

Here's the surprising part: while these cytokines typically promote inflammation, in this context they also drive the induction and expansion of regulatory T-cells. The research confirmed this effect through both laboratory and in-vivo analyses, demonstrating that the therapy has essentially hijacked a naturally occurring pathway to promote immune tolerance .

"Importantly, this study identified a naturally occurring pathway that our bodies and our immune systems have developed to allow for peripheral self-tolerance, and this therapy has taken advantage of that apoptotic cell clearance pathway mechanism," explained Joseph Podojil, research associate professor of Microbiology-Immunology.

Joseph Podojil, Research Associate Professor of Microbiology-Immunology at Northwestern Medicine

The scientists also discovered an increase in anti-inflammatory dendritic cells, which are specialized immune cells that present antigens on their surface to initiate immune responses. These dendritic cells appear to play a key role in driving the regulatory T-cell response, though researchers are still investigating exactly how they interact with these tolerance-promoting cells .

How to Understand the Key Mechanisms Behind This Immune Therapy

• Nanoparticle Uptake: Myeloid cells in the immune system engulf the biodegradable nanoparticles through a natural process called phagocytosis, which is how immune cells normally clear foreign material from the body.
• Apoptotic Cell Death: The breakdown of nanoparticles triggers controlled cell death that releases oxidized DNA, activating the STING pathway, a natural immune signaling system that the body uses to coordinate immune responses.
• Regulatory T-Cell Induction: Type-I interferons released through STING pathway activation drive the creation and expansion of regulatory T-cells, which actively suppress inflammatory responses against self-antigens in an antigen-specific manner.
• Dendritic Cell Involvement: Anti-inflammatory dendritic cells increase in number and appear to facilitate the development of regulatory T-cells, though their precise functional role is still being investigated.

What makes this approach fundamentally different from current treatments is its specificity. Rather than broadly suppressing the entire immune system, the nanoparticle therapy induces tolerance to specific antigens, meaning it targets only the problematic immune response while leaving the rest of your immune defenses intact .

"Consequently, we induce these regulatory T-cell populations that inhibit inflammatory response against a self-antigen and inhibit autoimmune responses in an antigen-specific manner," noted Joseph Podojil.

Joseph Podojil, Research Associate Professor of Microbiology-Immunology at Northwestern Medicine

What Questions Remain About This Treatment?

While the mechanisms are now clearer, researchers have identified several critical questions that need answering before this therapy can be widely deployed in clinical practice. The team plans to investigate the functional activity of the dendritic cells more deeply and determine how they interact with regulatory T-cell populations to drive tolerance .

Perhaps most importantly, scientists need to understand how long the treatment-induced tolerance actually lasts. This durability question is essential for developing clinical protocols and determining how frequently patients would need treatment. As Podojil explained, understanding the longevity of the induced tolerance could help inform the optimal treatment schedule for patients .

The research was led by Stephen Miller, professor emeritus of Microbiology-Immunology at Northwestern Medicine, and supported by grants from the National Institutes of Health, the Johnnie Walkers MS Foundation, and several private foundations dedicated to autoimmune disease research . This work represents a significant step toward developing more targeted, safer treatments for the millions of people living with autoimmune diseases worldwide.