Researchers at Karolinska Institutet have uncovered how serotonin-related metabolism helps regulate a under studied immune cell involved in allergic inflammation. The study, published in the journal Allergy, adds new knowledge about how allergic immune responses may be maintained over time.
Allergic diseases such as asthma are caused by complex immune reactions in the body. While much research has focused on a few well‑known immune cells such as type 2 helper T cells (Th2) and innate lymphoid cells (ILC2s), others have received far less attention. In a new study, researchers at Karolinska Institutet have examined type 2 cytotoxic T cells (Tc2), a type of immune cell increasingly linked to allergic disease.
Metabolism supports allergic inflammation
Tc2 cells are part of the immune system's type 2 response and can contribute to inflammation in allergies. The researchers found that these cells rely on specific metabolic pathways, including pathways related to serotonin, to sustain their inflammatory activity.
"Our study shows that Tc2 cells depend on lipid metabolism as well as the breakdown of serotonin, to function," says Chris Tibbitt , researcher at the Department of medicine, Huddinge , Karolinska Institutet.
"These new findings highlight that Tc2 cells have distinct and unique biological requirements that may influence how allergic inflammation develops and persists."
Early findings with future relevance
In collaboration with the BAMSE cohort , the study also observed altered Tc2 responses and lower prevalence of allergic sensitisation in individuals who had been prescribed selective serotonin reuptake inhibitors, SSRIs. According to the researchers, these preliminary observations need further investigation.
"Tc2 cells remain far less studied than other allergy‑associated immune cells, despite growing evidence of their role in diseases like asthma," says Chris Tibbitt. "By learning more about how these cells are regulated, we can improve our understanding of allergic inflammation."
The findings are at an early stage and have no immediate medical application. However, the researchers believe that increased knowledge about Tc2 cells may, over time, contribute to improved ways of identifying or targeting harmful type 2 inflammation in allergic disease.
The study was carried out in collaboration with other researchers at Karolinska Institutet and supported by the Swedish Research Council (VR), the Swedish Society for Allergology (SFFA), the Konsul Bergh Foundation and the Centre for Innovative Medicine (CIMED).
Publication
Serotonin Degradation and Lipid Metabolism Regulate Human Tc2 Cell Effector Functions.
de Souza Ferreira S, Holla L, Björkander S, Bek MK, Wirth L, Shearer PA, Säfholm J, Sachs E, Al-Ameri M, Vali K, Ekström S, Melén E, Mjösberg J, Tibbitt CA. Allergy, online 1 July 2026.
