Switching between defense and attack -- immune cells with dual role

As part of the innate immune system, dendritic cells are in the body's first line of defense against infections. They detect pathogens and coordinate the immune response. An international team led by Professor Barbara Schraml from LMU's Biomedical Center has now carried out an extensive study of a new type of dendritic cell and uncovered its important role in the body's immune response.

As the researchers demonstrate, dendritic cells that are marked by expression of the transcription factor RORγt -- so-called RORγt+ dendritic cells (DCs) -- are found in many tissues. Moreover, they have been conserved across many species in the course of evolution, which suggests they have essential functions. "We already knew that these cells maintain balance in the immune system and prevent overreactions," explains Schraml. "Now we've discovered that they can act flexibly and actively trigger immune reactions. Therefore, they appear to play a crucial role in our immune system."

Under normal conditions, RORyt+ DCs help prevent the immune system from attacking harmless things, like our gut bacteria or food components. But in times of infection or inflammation, they can switch roles and activate other immune cells. Of particular interest, the authors note, is the demonstration that these cells also appear to be involved in diseases like multiple sclerosis. In patients with multiple sclerosis, they take on an aggressive profile, suggesting they contribute to inflammation in the brain and spinal cord.

The dual functionality of RORγt+ DCs also opens the door to new treatment possibilities. For example, the cells could be targeted either to calm down an overactive immune system or to boost the immune system. "This makes them an attractive target for new therapies aimed at treating autoimmune diseases, enhancing vaccines, supporting cancer immunotherapy, or treating allergies," explains Schraml.