New thesis on MAIT cells provides insights into immunity and COVID-19

Tobias Kammann from the Center for Infectious Medicine (CIM) at the Department of Medicine, Huddinge (MedH) is defending his thesis titled “The diversity of MAIT cells across the human body and in COVID-19,” on 29 November, 2024. His main supervisor is Johan Sandberg (MedH).

What is the main focus of your thesis?

My research explored the roles of a special group of immune cells called mucosal-associated invariant T (MAIT) cells. These cells were discovered relatively recently and most of what we know about them stems from research on blood samples.

In my thesis, we investigated these cells in detail in human tissues donated to research, which allowed us to characterize the role of this cell type in different parts of the human body, such as the liver, the lung, and the intestines. Also, we investigated the involvement of MAIT cells in severe COVID-19 and how these cells recover in people recovering from the disease.

Which are the most important results?

For the first time, we could quantify the number of MAIT cells across paired blood and multiple organs from the same individual. We observed tissue-dependent distribution patterns and signs of specialization to the tissue environment.

In studies of hospitalized COVID-19 patients, we observed that MAIT cells were highly activated and migrating to the inflamed lung. In the aftermath of COVID-19, multiple months after recovery and release from the hospital, we detected that in some individuals, MAIT cells still displayed phenotypic alterations and functional impairment.

How can this new knowledge contribute to the improvement of people’s health?

Studying MAIT cells simultaneously in multiple healthy human tissues allowed us to lay out a landscape of these cells for the human tissue immunology and MAIT cell research community. A better understanding of the presence and roles of tissue-resident MAIT cells can lead to novel or improved strategies to treat a broad range of diverse human immune-related diseases.

Our findings on MAIT cells in COVID-19 suggest that MAIT cell activation can be an indicator for patients at higher risk of severe disease.

What are your future ambitions?

When considering the location of the immune system, you might instinctively think of the blood. However, the majority of our immune system actually resides outside of the blood, within our tissues, and we understand much less about it there. I would like to continue working on changing that and keep on exploring human tissue-resident T cell immunity.