Obesity impairs key immune cells but bariatric surgery reverses damage

New Maynooth University (MU) research led by the Department of Biology's Dr Ciara Flynn, working within the research group of Prof Andrew Hogan at the Kathleen Lonsdale Institute for Human Health Research has found that obesity can impair key immune cells that help protect the body against infection and cancer.

The study, published in JCI Insight, also found that bariatric surgery can reverse many of these immune cell defects, restoring their ability to respond more effectively to threats.

More than one billion adults worldwide live with obesity, which is linked to a greater risk of severe outcomes from viral and bacterial infections. During the COVID-19 pandemic, for example, people living with obesity faced a significantly higher risk of serious illness.

The study helps explain this heightened vulnerability by examining gamma delta (γδ) T cells, a specialised group of immune cells, particularly a subset called Vδ2+ T cells.

These cells are part of the body's first line of defence. They respond rapidly to infection and help identify and destroy certain cancer cells.

Researchers found that people living with obesity had fewer Vδ2+ T cells in their blood and that the cells were less active when stimulated. The cells also showed abnormalities in the processes that control nutrient uptake and energy production, both of which are essential to an effective immune response.

The findings indicate that obesity disrupts the cells' metabolism, limiting the energy available to respond to infection and disease.

Crucially, the immune cell defects were reversed following Roux-en-Y gastric bypass (RYGB) surgery. Patients showed significant improvements in the metabolic processes that support immune cell function, together with a marked recovery in the cells' ability to respond.

The research was conducted in collaboration with Prof Helen Heneghan and Prof Donal O'Shea at St Vincent's University Hospital and University College Dublin, and was funded by the Health Research Board.

Prof Andrew Hogan, Principle Investigator with the Obesity Immunology Research Group at Maynooth University's Department of Biology, said: 'The findings provide new insight into the relationship between obesity and immune dysfunction, helping to further explain why people living with obesity may be more vulnerable to serious infections, and a range of other conditions.

They also highlight that obesity is limiting immune cells metabolism, essentially leaving it without the energy it needs to protect us.'

Professor Paul Moynagh, Director of the Kathleen Lonsdale Institute for Human Health Research at Maynooth University, said: "This study is an excellent example of highly impactful translational research.

It has been achieved by Professors Hogan and Heneghan bringing their scientific and clinical expertise together to provide new insights into how obesity and its treatment affect the immune system in fighting infections and cancer."

Prof Helen Heneghan, Consultant Bariatric Surgeon at St Vincent's University Hospital, said: 'Our study highlights that successful treatment of obesity, with RYGB Surgery, reverses this immune dysfunction caused by obesity.

Essentially RYGB surgery restores the body's defences against infections and cancer, and helps explain why patients who have had bariatric surgery have a 40-50% lower chance of developing cancer and other obesity complications.'