To better fight disease, there’s much we still need to learn about the intricacies of the immune system. Now Australian scientists have learned the secrets of a special type of immune cell.
A team of researchers from the Peter Doherty Institute for Infection and Immunity in Melbourne are investigating how certain infection-fighting cells are produced in the body and how they can be harnessed to strengthen the body’s defences. The study was published today in Nature Immunology.
Tucked behind the lungs, the thymus gland is a small organ that’s part of the lymphatic system. It’s a factory and maturation site for T cells, a subtype of the white blood cells that participate in our immune system.
A large part of this system is made up of MAIT cells (mucosal-associated invariant T cells), but until now not much was known about their development and function.
Using mice models and human samples, University of Melbourne PhD candidate Hui-Fern Koay with supervisors Dr Daniel Pellicci and Professor Dale Godfrey have honed in on three distinct stages of MAIT cell development in the thymus.
Koay likens the three developmental stages of MAIT cells to “primary school, high school and university,” where the cells learn how to fight infections before entering circulation.
“Like real students, the very early cells don’t do very much, their sole purpose is to get educated,” Koay tells SBS Science. “Later on, once they’ve sort-of graduated in that analogy, they can go out to the big city and do the important job of fighting infections and being fully functional."
“It is important to understand how different classes of immune cells work so that we can turn on the correct immune response ‘program’ by vaccines and form effective immunity,” says Dr Kim Jacobson, an immunology expert from Monash University who wasn’t involved in the study.
Harnessing cells for new therapies
Researchers recently discovered that, unlike other T cells in the immune system that recognise infections through protein or lipid markers, MAIT cells can detect vitamin B metabolites that can be a sign of bacterial infection.
“The biggest distinguishing factor is what [MAIT cells] recognise, the molecules they recognise, I think that was a bit of the puzzle that was missing from our immune system,” says Koay, explaining that a logical step in the process of figuring out more about these cells is to look at their development.
The research team discovered a series of ‘checkpoints’ that control cell progress through the developmental stages, which lets researchers determine what helps MAIT cell growth and increase in numbers. This could ultimately help to manipulate them into fighting infections or creating new immunotherapy treatments for cancer.
According to Jacobson, changes in MAIT cell numbers have also been linked to poor health outcomes in autoimmune diseases such as diabetes, so it makes sense to investigate ways of controlling how they act in the body.
“The research has opened up new, sophisticated ways to assess if the normally protective MAIT cells are driven to harm the body in these conditions,” she says.
The next step for the team will be to investigate the various factors that control MAIT cell populations and how these can be accurately manipulated without harming other immune cells.