Tag Archives: rheumatoid arthritis

Nanoparticle treatment for rheumatoid arthritis

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An October 26, 2023 news item on phys.org announced a possible new treatment for rheumatoid arthritis (RA), Note: Links have been removed,

A team of scientists [Korea] has developed a new solution for the treatment of rheumatoid arthritis (RA). The work has been published in Nature Nanotechnology.

RA is a chronic disease that, unfortunately, has no cure. The disease triggers a mix of troublesome symptoms like inflamed joints, harmful cytokines, and immune system imbalances, which work together to create a relentless cycle of worsening symptoms. While targeting some of these factors can provide short-term relief, others remain unresolved, leading to a frustrating cycle of remission and flare-ups.

One of the major hurdles in RA treatment is the inability to restore the immune system to its healthy state. This leaves the body unable to control the continuous production of harmful substances like reactive oxygen species (ROS) and inflammatory cytokines, leading to persistent inflammation and discomfort.

In essence, the ideal treatment for RA should not only provide immediate relief from inflammation and symptoms but also address the root cause by restoring the immune system to its normal, balanced state.

New nanoparticle-based system as a solution

The new platform involves immobilizing ceria nanoparticles (Ce NPs) onto mesenchymal stem cell-derived nanovesicles (MSCNVs). Both of these components can hinder different pathogenic factors, allowing them to work both individually and cooperatively to achieve a comprehensive treatment.

…

Caption: Schematic illustration of comprehensive and combination RA therapy by Ce-MSCNV nanoparticles. Ce-MSCNVs scavenge the over-produced ROS in an RA knee joint, induce M1 to M2 macrophage polarization for immediate relief of inflammation and symptoms, modulate DCs into tDCs, and finally induce Tregs. Credit: Institute for Basic Science

An October 27, 2023 Institute for Basic Science (IBS) press release (also on EurekAlert but published October 26, 2023), which originated the news item, provides more details about the proposed treatment,

Ce NPs – can scavenge the overproduced ROS in RA-inflicted knee joints. They also induce polarization of M1 macrophages into M2, achieving immediate relief of inflammation and symptoms.

MSCNVs – deliver immunomodulatory cytokines, which turn dendritic cells (DC) into tolerogenic dendritic cells (tDCs). This consequently generates regulatory T cells for long-term immune tolerance.

In short, this approach aims to bridge both innate and adaptive immunity to achieve both short-term pain relief, as well as convert the tissue environment into an immune-tolerant state to prevent the recurrence of symptoms.

Researchers confirmed the efficacy of this approach using a collagen-induced arthritis mouse model. The Ce-MSCNV system was able to comprehensively treat and prevent RA by simultaneously relieving the immediate and restoring T cell immunity. Supporting data suggest that improvement in conditions can be achieved after only a single-dose treatment.

The mice treated with the Ce-MSCNV combination fared far better compared to the ones only treated using the Ce NP or MSCNV group. This clearly demonstrates the synergy between anti-inflammation and immunomodulation and underlines the importance of the combined therapy for effective RA treatment. In addition, Ce-MSCNV administration prior to booster injection markedly reduced the incidence and severity of symptoms, supporting the prophylactic potential of these nanoparticles.

First author KOO Sagang stated, “One of the hardest decisions in intractable disease therapy is determining how long the treatment should be carried on. For RA, it would not be appropriate to stop treatment just because the target marker is stabilized. A safer indicator should be that the innate and adaptive components of the collapsed immune system are normalized to protect the body.”

Koo believes that the strategy adopted by Ce-MSCNVs, where different treatment mechanisms work together, provides a unique advantage in this regard. Furthermore, she predicts that a similar approach would also be applicable to other intractable, inflammatory, and autoimmune diseases for this purpose. The components within the system may also be modified. For example, other catalysts for generating ROS or other cell-derived nanovesicles could be utilized depending on the types of diseases. Overall, this study proves the potential of a hybrid nanoparticle system for the comprehensive treatment of autoimmune disease and modulation of the immune system.

Here’s a link to and a citation for the paper,

Ceria-vesicle nanohybrid therapeutic for modulation of innate and adaptive immunity in a collagen-induced arthritis model by Sagang Koo, Hee Su Sohn, Tae Hee Kim, Siyeon Yang, Se Youn Jang, Seongryeol Ye, Boomin Choi, Soo Hyeon Kim, Kyoung Sun Park, Hyun Mu Shin, Ok Kyu Park, Cheesue Kim, Mikyung Kang, Min Soh, Jin Yoo, Dokyoon Kim, Nohyun Lee, Byung-Soo Kim, Youngmee Jung & Taeghwan Hyeon. Nature Nanotechnology (2023) DOI: https://doi.org/10.1038/s41565-023-01523-y Published: 26 October 2023

This paper is behind a paywall.

Alleviating joint damage and inflammation from arthritis with neutrophil nanosponges

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Assuming you’d be happy with limiting the damage for rheumatoid arthritis, at some point in the future, this research looks promisin. Right now it appears the researchers aren’t anywhere close to a clinical trial. From a Sept. 3, 2018 news item on ScienceDaily,

Engineers at the University of California San Diego [UCSD] have developed neutrophil “nanosponges” that can safely absorb and neutralize a variety of proteins that play a role in the progression of rheumatoid arthritis. Injections of these nanosponges effectively treated severe rheumatoid arthritis in two mouse models. Administering the nanosponges early on also prevented the disease from developing.

A Sept. 3, 2018 UCSD press release (also on EurekAlert), which originated the news item, provides more detail,

“Nanosponges are a new paradigm of treatment to block pathological molecules from triggering disease in the body,” said senior author Liangfang Zhang, a nanoengineering professor at the UC San Diego Jacobs School of Engineering. “Rather than creating treatments to block a few specific types of pathological molecules, we are developing a platform that can block a broad spectrum of them, and this way we can treat and prevent disease more effectively and efficiently.”

This work is one of the latest examples of therapeutic nanosponges developed by Zhang’s lab. Zhang, who is affiliated with the Institute of Engineering in Medicine and Moores Cancer Center at UC San Diego, and his team previously developed red blood cell nanosponges to combat and prevent MRSA infections and macrophage nanosponges to treat and manage sepsis.

neutrophil nanosponge cartoon
Illustration of a neutrophil cell membrane-coated nanoparticle.

The new nanosponges are nanoparticles of biodegradable polymer coated with the cell membranes of neutrophils, a type of white blood cell.

Neutrophils are among the immune system’s first responders against invading pathogens. They are also known to play a role in the development of rheumatoid arthritis, a chronic autoimmune disease that causes painful inflammation in the joints and can ultimately lead to damage of cartilage and bone tissue.

When rheumatoid arthritis develops, cells in the joints produce inflammatory proteins called cytokines. Release of cytokines signals neutrophils to enter the joints. Once there, cytokines bind to receptors on the neutrophil surfaces, activating them to release more cytokines, which in turn draws more neutrophils to the joints and so on.

The nanosponges essentially nip this inflammatory cascade in the bud. By acting as tiny neutrophil decoys, they intercept cytokines and stop them from signaling even more neutrophils to the joints, reducing inflammation and joint damage.

These nanosponges offer a promising alternative to current treatments for rheumatoid arthritis. Some monoclonal antibody drugs, for example, have helped patients manage symptoms of the disease, but they work by neutralizing only specific types of cytokines. This is not sufficient to treat the disease, said Zhang, because there are so many different types of cytokines and pathological molecules involved.

“Neutralizing just one or two types might not be as effective. So our approach is to take neutrophil cell membranes, which naturally have receptors to bind all these different types of cytokines, and use them to manage an entire population of inflammatory molecules,” said Zhang.

“This strategy removes the need to identify specific cytokines or inflammatory signals in the process. Using entire neutrophil cell membranes, we’re cutting off all these inflammatory signals at once,” said first author Qiangzhe Zhang, a Ph.D. student in Professor Liangfang Zhang’s research group at UC San Diego.

To make the neutrophil nanosponges, the researchers first developed a method to separate neutrophils from whole blood. They then processed the cells in a solution that causes them to swell and burst, leaving the membranes behind. The membranes were then broken up into much smaller pieces. Mixing them with ball-shaped nanoparticles made of biodegradable polymer fused the neutrophil cell membranes onto the nanoparticle surfaces.

“One of the major challenges of this work was streamlining this entire process, from isolating neutrophils from blood to removing the membranes, and making this process repeatable. We spent a lot of time figuring this out and eventually created a consistent neutrophil nanosponge production line,” said Qiangzhe Zhang.

In mouse models of severe rheumatoid arthritis, injecting nanosponges in inflamed joints led to reduced swelling and protected cartilage from further damage. The nanosponges performed just as well as treatments in which mice were administered a high dose of monoclonal antibodies.

The nanosponges also worked as a preventive treatment when administered prior to inducing the disease in another group of mice.

Professor Liangfang Zhang cautions that the nanosponge treatment does not eliminate the disease. “We are basically able to manage the disease. It’s not completely gone. But swelling is greatly reduced and cartilage damage is minimized,” he said.

The team hopes to one day see their work in clinical trials.

Here’s a link to and a citation for the paper,

Neutrophil membrane-coated nanoparticles inhibit synovial inflammation and alleviate joint damage in inflammatory arthritis by Qiangzhe Zhang, Diana Dehaini, Yue Zhang, Julia Zhou, Xiangyu Chen, Lifen Zhang, Ronnie H. Fang, Weiwei Gao, & Liangfang Zhang. Nature Nanotechnology (2018) DOI: https://doi.org/10.1038/s41565-018-0254-4 Published 03 September 2018

This paper is behind a paywall.

Hallucinogenic molecules and the brain

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Psychedelic drugs seems to be enjoying a ‘moment’. After decades of being vilified and  declared illegal (in many jurisdictions), psychedelic (or hallucinogenic) drugs are once again being tested for use in therapy. A Sept. 1, 2017 article by Diana Kwon for The Scientist describes some of the latest research (I’ve excerpted the section on molecules; Note: Links have been removed),

Mind-bending molecules

© SEAN MCCABE

All the classic psychedelic drugs—psilocybin, LSD, and N,N-dimethyltryptamine (DMT), the active component in ayahuasca—activate serotonin 2A (5-HT2A) receptors, which are distributed throughout the brain. In all likelihood, this receptor plays a key role in the drugs’ effects. Krähenmann [Rainer Krähenmann, a psychiatrist and researcher at the University of Zurich]] and his colleagues in Zurich have discovered that ketanserin, a 5-HT2A receptor antagonist, blocks LSD’s hallucinogenic properties and prevents individuals from entering a dreamlike state or attributing personal relevance to the experience.12,13

Other research groups have found that, in rodent brains, 2,5-dimethoxy-4-iodoamphetamine (DOI), a highly potent and selective 5-HT2A receptor agonist, can modify the expression of brain-derived neurotrophic factor (BDNF)—a protein that, among other things, regulates neuronal survival, differentiation, and synaptic plasticity. This has led some scientists to hypothesize that, through this pathway, psychedelics may enhance neuroplasticity, the ability to form new neuronal connections in the brain.14 “We’re still working on that and trying to figure out what is so special about the receptor and where it is involved,” says Katrin Preller, a postdoc studying psychedelics at the University of Zurich. “But it seems like this combination of serotonin 2A receptors and BDNF leads to a kind of different organizational state in the brain that leads to what people experience under the influence of psychedelics.”

This serotonin receptor isn’t limited to the central nervous system. Work by Charles Nichols, a pharmacology professor at Louisiana State University, has revealed that 5-HT2A receptor agonists can reduce inflammation throughout the body. Nichols and his former postdoc Bangning Yu stumbled upon this discovery by accident, while testing the effects of DOI on smooth muscle cells from rat aortas. When they added this drug to the rodent cells in culture, it blocked the effects of tumor necrosis factor-alpha (TNF-α), a key inflammatory cytokine.

“It was completely unexpected,” Nichols recalls. The effects were so bewildering, he says, that they repeated the experiment twice to convince themselves that the results were correct. Before publishing the findings in 2008,15 they tested a few other 5-HT2A receptor agonists, including LSD, and found consistent anti-inflammatory effects, though none of the drugs’ effects were as strong as DOI’s. “Most of the psychedelics I have tested are about as potent as a corticosteroid at their target, but there’s something very unique about DOI that makes it much more potent,” Nichols says. “That’s one of the mysteries I’m trying to solve.”

After seeing the effect these drugs could have in cells, Nichols and his team moved on to whole animals. When they treated mouse models of system-wide inflammation with DOI, they found potent anti-inflammatory effects throughout the rodents’ bodies, with the strongest effects in the small intestine and a section of the main cardiac artery known as the aortic arch.16 “I think that’s really when it felt that we were onto something big, when we saw it in the whole animal,” Nichols says.

The group is now focused on testing DOI as a potential therapeutic for inflammatory diseases. In a 2015 study, they reported that DOI could block the development of asthma in a mouse model of the condition,17 and last December, the team received a patent to use DOI for four indications: asthma, Crohn’s disease, rheumatoid arthritis, and irritable bowel syndrome. They are now working to move the treatment into clinical trials. The benefit of using DOI for these conditions, Nichols says, is that because of its potency, only small amounts will be required—far below the amounts required to produce hallucinogenic effects.

In addition to opening the door to a new class of diseases that could benefit from psychedelics-inspired therapy, Nichols’s work suggests “that there may be some enduring changes that are mediated through anti-inflammatory effects,” Griffiths [Roland Griffiths, a psychiatry professor at Johns Hopkins University] says. Recent studies suggest that inflammation may play a role in a number of psychological disorders, including depression18 and addiction.19

“If somebody has neuroinflammation and that’s causing depression, and something like psilocybin makes it better through the subjective experience but the brain is still inflamed, it’s going to fall back into the depressed rut,” Nichols says. But if psilocybin is also treating the inflammation, he adds, “it won’t have that rut to fall back into.”

…

If it turns out that psychedelics do have anti-inflammatory effects in the brain, the drugs’ therapeutic uses could be even broader than scientists now envision. “In terms of neurodegenerative disease, every one of these disorders is mediated by inflammatory cytokines,” says Juan Sanchez-Ramos, a neuroscientist at the University of South Florida who in 2013 reported that small doses of psilocybin could promote neurogenesis in the mouse hippocampus.20 “That’s why I think, with Alzheimer’s, for example, if you attenuate the inflammation, it could help slow the progression of the disease.”

For anyone who was never exposed to the anti-hallucinogenic drug campaigns, this turn of events is mindboggling. There was a great deal of concern especially with LSD in the 1960s and it was not entirely unfounded. In my own family, a distant cousin, while under the influence of the drug, jumped off a building believing he could fly.  So, Kwon’s story opening with a story about someone being treated successfully for depression with a psychedelic drug was surprising to me . Why these drugs are being used successfully for psychiatric conditions when so much damage was apparently done under the influence in decades past may have something to do with taking the drugs in a controlled environment and, possibly, smaller dosages.

Selecta Biosciences’ proprietary tolerogenic nanoparticles improve efficacy and safety of biologic drugs

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Although it may not seem like it initially, there is a nanotechnology element to this piece of news. From an Aug. 1, 2016 news item on Nanotechnology Now ,

Selecta Biosciences, Inc. (NASDAQ: SELB), a clinical-stage biopharmaceutical company developing targeted antigen-specific immune therapies for rare and serious diseases, announced today that Nature Nanotechnology has published an article that presents preclinical results from Selecta’s research which demonstrate the broad potential applicability of Selecta’s novel immune tolerance platform. Details that elucidate the mechanism of action of the company’s immune tolerance therapy, SVP [Synthetic Vaccine Particle]-Rapamycin (SEL-110), were also shown. Data in the publication support the Company’s lead clinical program, showing Selecta’s SVP-Rapamycin (SEL-110) induces antigen-specific immune tolerance and mitigates the formation of anti-drug antibodies (ADAs) to biologic drugs, including pegsiticase (for gout) and adalimumab (for rheumatoid arthritis).

An Aug. 1, 2016 Selecta Biosciences news release (also on EurekAlert), which originated the news item, provides more information,

“Undesired immune responses affect both the efficacy and safety of marketed biologic therapies and the development of otherwise promising new technologies. Selecta’s SVP platform positions the company to enhance biologic therapy and to advance a pipeline of proprietary products that meet the therapeutic needs of patients with rare and serious diseases,” said Werner Cautreels, PhD,Chairman of the Board, CEO and President of Selecta Biosciences. “This publication in Nature Nanotechnology highlights the mechanism by which Selecta’s proprietary nanoparticles induce lasting antigen-specific tolerance. We believe that SVP-Rapamycin has the potential to mitigate ADAs against a broad range of biologic therapies.”

In the Nature Nanotechnology journal article, Selecta presents validation of the immune tolerance mechanism of action of the company’s technology, demonstrating that poly(lactic-co-glycolic acid) (PLGA) nanoparticles encapsulating rapamycin, but not free rapamycin, are capable of inducing durable immunological tolerance to co-administered proteins. This robust immune tolerance is characterized immunologically by: (1) induction of tolerogenic dendritic cells; (2) an increase in regulatory T cells; (3) reduction in B cell activation and germinal center formation; and (4) inhibition of antigen-specific hypersensitivity reactions.

Data presented in the journal article support the Company’s clinical lead program in gout, showing that intravenous co-administration of tolerogenic nanoparticles with pegylated uricase inhibited the formation of ADAs in mice and nonhuman primates and normalized serum uric acid levels in uricase-deficient mice. Underscoring the broad potential of the approach, results additionally show that subcutaneous co-administration of nanoparticles with adalimumab durably inhibited ADAs, resulting in normalized pharmacokinetics of the anti-TNFα antibody and protection against arthritis in TNFα transgenic mice.

In the published research, the induction of specific immune tolerance by SVP-Rapamycin (SEL-110) versus chronic immune suppression is supported by the findings that: (1) antigen must be co-administered at the time of SVP-Rapamycin (SEL-110) treatment; (2) immune tolerance is durable to many challenges of antigen alone; (3) animals tolerized to a specific antigen are capable of responding to an unrelated antigen, meaning that SVP-Rapamycin (SEL-110) does not induce a broad immune suppression; and (4) activation of naïve T cells is inhibited when adoptively transferred into previously tolerized mice. In contrast, daily administration of free rapamycin, at five times the total weekly rapamycin dose as that administered in the SVP-Rapamycin, was observed to transiently suppress the immune response, but did not induce durable immunological tolerance.

Here’s a link to and a citation for the paper,

Improving the efficacy and safety of biologic drugs with tolerogenic nanoparticles by Takashi K. Kishimoto, Joseph D. Ferrari, Robert A. LaMothe, Pallavi N. Kolte, Aaron P. Griset, Conlin O’Neil, Victor Chan, Erica Browning, Aditi Chalishazar, William Kuhlman, Fen-ni Fu, Nelly Viseux, David H. Altreuter, Lloyd Johnston, & Roberto A. Maldonado. Nature Nanotechnology (2016)  doi:10.1038/nnano.2016.135 Published online 01 August 2016

This paper is behind a paywall.

Parvus Therapeutics (Calgary, Canada) and reprogramming immune cells

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An international collaboration of Canadian, Spanish, and US scientists has announced a new therapeutic approach which could reverse autoimmune diseases in a Feb. 17, 2016 news item on Nanotechnology Now,

• Nanotechnology Approach Restores Glucose Regulation and Motor Function in In Vivo Preclinical Models of Diabetes and Multiple Sclerosis, Respectively; Joint Swelling and Destruction Resolved in In Vivo Model of Rheumatoid Arthritis
• Parvus’ Approach Can Be Tailored to Treat Diverse Diseases

A Feb. 17, 2016 Parvus Therapeutics news release (also on EurekAlert), which originated the news item, provides more detail and a strong orientation to marketing communication,

Parvus Therapeutics today announced the publication in Nature of a seminal paper describing the discovery and applications of a novel therapeutic approach employing nanomedicines, referred to as “Navacims”TM, to reprogram white blood cells to become regulatory cells capable of blunting autoimmune responses and restoring the equilibrium of the immune system. Navacims are nanoparticles (NPs) coated with disease-relevant peptide-major histocompatibility complexes (pMHCs) that alter the behavior of pathogenic T lymphocytes by binding directly to their antigen receptors. The peer-reviewed article, titled “Expanding antigen-specific regulatory networks to treat autoimmunity” reports on a body of work, including results in multiple in vivo disease models, built on more than eight years of research by Parvus Founder and Chief Scientific Officer, Pere Santamaria, M.D., Ph.D.

Dr. Santamaria commented, “Autoimmune diseases, including type 1 diabetes, multiple sclerosis, and rheumatoid arthritis, are extraordinarily complex responses of our immune system against some of our own tissues (e.g. pancreas, brain and joints, respectively), leading to chronic organ inflammation, organ dysfunction, and, in some cases, premature death. Blunting these incompletely understood immune responses without suppressing the normal components of our immune system that protect us against infection and cancer is not currently possible.”

“However, our work offers a pharmaceutical solution to this fundamental problem,” Dr. Santamaria continued. “Navacims essentially re-program disease-causing white blood cells to become disease-suppressing cells, known as regulatory cells, leading to sustained therapeutic effects in various spontaneous and experimental autoimmune diseases, as reported in our article in Nature. Essentially, we have found that Navacims can be tailored to treat a wide range of autoimmune diseases, while sharing a common structure. Importantly, they have been shown to affect human white blood cells in the same manner as they do murine cells. Furthermore, Navacims have shown promising safety findings in preclinical in vivo models. Based on our results to date, we believe Navacims represent a therapeutic platform with broad-ranging health care implications.”

Findings being reported in Nature include:

pMHC class II Navacims expanded cognate CD4+ T-cells that consistently have a TR1-like, regulatory T cell surface phenotype, transcriptional pattern and cytokine profile (mouse=human TR1 cells) systemically.

pMHC class II-Navacims designed to target T cells in newly diabetic nonobese (NOD) mice restored normoglycemia (normal blood sugar regulation) in the majority of the mice tested.

Tailored pMHC class II Navacims restored motor function to paralyzed C57BL/6 mice at the peak of Experimental Autoimmune Encephalomyelitis (a model of Multiple Sclerosis).

pMHC class II Navacims, targeting disease-causing T cells in joints, resolved joint swelling and destruction in arthritic mice.

“The findings being reported in Nature represent a scientific advance for Parvus and also a major achievement in the field of Immunology,” said Janice M. LeCocq, CEO of Parvus. “We believe that Dr. Santamaria’s work has the potential to transform the treatment of many of the more than 80 major autoimmune diseases affecting humankind, alleviating the suffering of millions of patients and their families. Over the coming year, we will be dedicating much of our in-house efforts to the advancement of our two lead programs for type 1 diabetes and multiple sclerosis.”

“Dr. Santamaria’s work to target the immune system dysfunction that causes type 1 diabetes represents the kind of innovative work that JDRF believes will eventually get us to a cure for this disease,” said Juvenile Diabetes Research Foundation Vice President of Discovery Research Julia Greenstein, Ph.D. “He and his colleagues have made exciting progress towards possibly developing a new class of drugs that could rebalance certain T-cells and ultimately provide a cure for type 1 diabetes and other autoimmune diseases as well.” The JDRF has funded the work of Dr. Santamaria and his colleagues at Parvus to explore Navacim-based treatments for diabetes.

Parvus’ strategy is to establish partnerships with major pharmaceutical companies to undertake the clinical and commercial development of many of its product pipeline candidates while also reserving rights to others suitable for its own development and commercialization. Parvus currently is engaged in late stage discussions with multiple pharmaceutical companies with regard to the type 1 diabetes (T1D) program. Manufacturing scale-up is now underway to supply upcoming preclinical and clinical studies.

The work being reported in Nature was led by Dr. Pere Santamaria and largely executed at the University of Calgary, Cumming School of Medicine (animal models of disease) and the Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) (humanized mouse work), with significant contributions from investigators at Institutions in Europe and the US. Further, Innovate Calgary, the technology-transfer and business-incubation center for the University of Calgary, provided early support for the transfer of the Navacims technology to and incubation of Parvus Therapeutics, which was organized as a separate entity in 2012.

It should be noted that this intervention has been tested on ‘humanized’ mice and, at this point, there don’t seem to have been any human clinical trials. At a guess I’d say we’re still several years away from this therapeutic intervention reaching the market, should it prove to be successful in humans.

Here’s a link to and a citation for the paper,

Expanding antigen-specific regulatory networks to treat autoimmunity by Xavier Clemente Casares, Jesus Blanco, Poornima Ambalavanan, Jun Yamanouchi, Santiswarup Singha, Cesar Fandos, Sue Tsai, Jinguo Wang, Nahir Garabatos, Cristina Izquierdo, Smriti Agrawal, Michael B. Keough, V. Wee Yong, Eddie James, Anna Moore, Yang Yang, Thomas Stratmann, Pau Serra, & Pere Santamaria. Nature (2016) doi:10.1038/nature16962 Published online 17 February 2016

This paper is behind a paywall.