Chicago, IL – August 12, 2026 – In a new study published today in Science Advances, Northwestern Medicine researchers have uncovered a previously hidden immune environment in the thymus that may help drive myasthenia gravis (MG), a chronic autoimmune disease that causes muscle weakness and fatigue, mainly impacting women under age 40 and men over age 60. Using the largest known cellular and spatial map of the MG thymus ever assembled, researchers identified specialized immune cells and survival signals that may help sustain the disease, opening new avenues for future research and treatment.

Myasthenia gravis occurs when the body's immune system mistakenly attacks the communication point between nerves and muscles. The symptoms worsen with activity and improve with rest. Most often, the disease affects the muscles that control the eyes, facial expressions, talking, swallowing and chewing. In severe cases, breathing muscles can become dangerously weak.

While researchers have long known that harmful antibodies play a major role in MG, they do not fully explain why symptoms vary among patients or why some people continue to experience disease activity despite treatment, including the surgical removal of the thymus called a thymectomy.

“During childhood, the purpose of the thymus is to train the body’s immune cells, but in adulthood, the thymus shrivels up and starts to malfunction, which can lead to myasthenia gravis,” said Ankit Bharat, MD, senior author of the study, chief of thoracic surgery and executive director of the Northwestern Medicine Canning Thoracic Institute. "Our study suggests there's more to myasthenia gravis than antibodies alone. We found evidence that the thymus may create an abnormal immune environment that helps certain B cells survive and persist, even after the thymus is removed. Understanding that environment gives us an entirely new framework for studying and possibly treating the disease."

What this means for patients

For patients like 30-year-old Marissa Humayun of Chicago, the latest research gives her hope, especially after three years of ups and downs.

In early 2023, at the age of 26, Humayun went to the emergency department with stroke-like symptoms that came out of nowhere, including a droopy eyelid and double vision. When bloodwork came back negative for the main MG antibodies, Neena Cherayil, MD, a neuro-ophthalmologist at Northwestern Medicine, diagnosed Humayun with ocular myasthenia gravis (OMG) and seronegative myasthenia, a rare form of MG, where three of the known antibodies for MG don’t show up in standard blood tests, but patients still present symptoms.

Three months after her diagnosis, Humayun underwent robotic surgery with Dr. Bharat to have her thymus removed and donated the small gland to his research study. Even though the thymectomy was a success, Humayun’s symptoms returned, which can happen in some patients. Humayun now relies on infusion therapy at Northwestern Memorial Hospital to help control her symptoms and is treated by Arjun Seth, MD, a neuromuscular medicine specialist at Northwestern Medicine.

“When symptomatic, I have droopy eyelids, fatigue and double vision – especially if I’ve pushed myself too hard or didn’t rest enough. Myasthenia gravis is such a discouraging disease, but I must honor my body for what it can do today,” said Humayun. “Dr. Bharat is an inspiring surgeon and researcher, and Northwestern Medicine has truly taken care of me throughout my diagnosis and treatment. I’m optimistic for the future, knowing scientists right here in Chicago are working to find solutions for patients in the myasthenia gravis community.”

“Our hope is that we can now identify patients – like Marissa – who are at risk of having a recurrence after the thymectomy and after treatment,” said Dr. Bharat. “Also, this study gives us clues as to why some patients don’t respond to the conventional medical treatments. What we’re hoping to do is identify those patients who are at risk and then ultimately design clinical interventions that can kill those cells and then prevent the recurrences.”

A surprising discovery

To better understand what happens inside the thymus, Northwestern Medicine researchers analyzed 23 thymus samples from 16 patients and combined several advanced technologies, including single-cell RNA sequencing, immune receptor analysis and spatial transcriptomics. Together, these techniques allowed scientists to identify individual cell types and determine where those cells were located within the tissue.

After integrating their data with previously published datasets, the team created an atlas containing nearly 347,000 cells, making it the most comprehensive map of the MG thymus to date. Researchers expected to find evidence of a single rogue immune-cell population driving disease, but instead, they found something very different.

The study revealed a diverse population of class-switched B cells clustered within and around abnormal germinal centers in MG tissue. Rather than showing signs of traditional immune regulation, these cells appeared to rely on a separate survival pathway involving molecules known as BAFF and BCMA.

The researchers describe the finding as a potential "tolerance checkpoint swap" in which B cells move away from normal immune-control mechanisms and become supported by survival signals from the surrounding tissue environment.

"We did not find one dominant B-cell clone taking over," said Dr. Bharat. "Instead, we found a diverse population of B cells living within an abnormal immune neighborhood. The neighborhood itself may be helping these cells survive."

What happens next?

The findings may help explain several longstanding mysteries surrounding myasthenia gravis, including why antibody levels do not always match disease severity and why improvement after thymus-removal surgery can vary from patient to patient. However, the researchers caution that the current study did not directly test those questions.

“This study is not a treatment announcement and does not change current recommendations for patients with myasthenia gravis,” said Dr. Bharat. “Thymectomy remains an evidence-based treatment for appropriately selected patients, and additional research will be required to determine whether the newly identified pathways play a direct role in disease progression.”

Instead, the work provides a detailed roadmap for future investigation.

"This study gives us a map," said Dr. Bharat. "The next step is to determine whether these pathways actively drive disease and whether they can be targeted to restore immune tolerance. That's the promise of this research."

The pulmonology and lung surgery program at Northwestern Memorial Hospital is proud to be the highest-ranked in Illinois for 15 straight years and No. 4 in the U.S., according to U.S. News & World Report, 2026 – 2027. For more information, visit nm.org.

CHICAGO – February 18, 2025 – How much can the eyes reveal about a person? A first-of-its-kind study from Northwestern Medicine and published in the Journal of Imaging is giving experts an idea how long COVID affects the body by looking through the eyes. The research could help doctors diagnose and track how the condition impacts people over time and provide insight into the cause of long COVID.

In the study, researchers used advanced imaging techniques to examine the retinas of non-hospitalized long COVID patients from the Northwestern Medicine Neuro COVID-19 Clinic and found that patients with long COVID experienced a significant reduction in the density of blood vessels in the back of the eye, compared to healthy individuals.

“This finding bridges gaps between ophthalmology, neurology, and COVID-19, helping us better understand how inflammation affects different organs in the body,” said Manjot K. Gill, MD, senior author of the study and ophthalmology lead of the Northwestern Medicine Comprehensive COVID-19 Center. “The change in blood vessels in the deep part of the retina supports the hypothesis that long COVID affects similar blood vessels in other parts of the body, like the brain, which can potentially contribute to the symptoms of long COVID such as memory loss, brain fog and fatigue.”

In patients with long COVID, researchers found that the most significant change was a decrease in blood flow in the smallest blood vessels in the deeper layers of the retina. Researchers believe this decrease in circulation may be reflective of decreased blood circulation in the brain, which may lead to neurologic symptoms.

“In oculomics – the field of study that examines the relationship between eye health and systemic diseases – we are understanding the power of the retina as a biomarker for disease, identifying early signs of diabetes, cardiovascular disease, and neurodegenerative disorders. It’s exciting to see how long COVID could fit into this framework,” said Dr. Gill. “Retinal imaging allows us to see the blood vessels that we cannot readily image elsewhere, so in this context, the eyes really are the ‘window to the soul.’”

Building on these findings, researchers are launching a longitudinal study that will examine how the changes in the deep retinal blood vessels relate to patient symptoms and other established markers of long COVID. They hope to determine if retinal imaging could be used as a tool to diagnose, manage and predict the progression of long COVID over time, as well as identify its cause.  

“Even though the immediate threat of the COVID-19 pandemic has decreased, approximately one-third of COVID-19 survivors experience lingering effects. This issue affects an estimated 17 million adults in the U.S. and comes with significant healthcare and economic burdens, costing about $600 million in lost wages,” said Igor Koralnik, MD, chief of neuroinfectious diseases and global neurology at Northwestern Medicine, who oversees the Neuro COVID-19 Clinic and is the co-director of the Northwestern Medicine Comprehensive COVID-19 Center. “There are currently no specific treatments for long COVID, and this research helps to advance our understanding of the condition. By studying the effects of COVID-19 on the body, we can improve diagnosis, management, and support for those affected.”

To date, the Neuro COVID-19 Clinic has cared for nearly 3,000 long-haulers from 44 states. For more information, visit nm.org and to schedule an appointment, please call 312.695.7950.