A common strep throat infection can trigger guttate psoriasis by altering the behaviour of key immune cells, according to a new study from Karolinska Institutet published in eBioMedicine. The findings suggest how an infection can lead to sudden skin inflammation, particularly in children and young adults.
In the study, the researchers analysed blood and skin samples from patients with guttate psoriasis using single‑cell technologies that allowed them to examine hundreds of thousands of individual immune cells in detail. The analysis showed that neutrophils, the most common type of immune cell, behave differently depending on their environment during a streptococcal infection.
Most striking was the discovery of a group of neutrophils with the ability to present antigens - fragments of pathogens that signal and guide other immune cells. These antigen‑presenting neutrophils accumulated in the affected skin of people with guttate psoriasis and were able to activate T cells, which may contribute to inflammation.
"Doctors have long known that strep throat can precede guttate psoriasis, but the biological explanation has been unclear," says Avinash Padhi , first author of the study and Research Specialist at the Department of Medicine, Solna . "Our findings suggest a link between infection and skin inflammation through the accumulation of antigen‑presenting neutrophils in patients' skin."
The researchers compared blood neutrophils from psoriasis patients with those from healthy individuals and from patients with severe strep‑related lung inflammation. This comparison helped identify what is unique to neutrophils in psoriasis.
How the cells communicate
They also examined how neutrophils communicate with other cells by analysing receptor-ligand interactions, the molecular signals cells use to coordinate immune responses.
"These results challenge the traditional view of neutrophils as simple first‑line defenders," says Magdalini Lourda , senior author of the study and senior research specialist at the Department of Laboratory Medicine . "They appear to have a wider role in shaping immune responses, which may be important when designing future treatments."
Next steps in the research
The next phase of the project is to validate the findings in larger and more diverse patient groups, including people with plaque psoriasis, to determine whether antigen‑presenting neutrophils can serve as predictive biomarkers or potential drug targets. The researchers also aim to clarify which molecular signals cause neutrophils to change behaviour and how they interact with T cells in early autoimmune inflammation.
This work was made possible through the efforts of Dr. Josefin Lysell , co-last author of the article and a dermatologist at Karolinska University Hospital, whose role in coordinating patient recruitment was instrumental.
The study was conducted in collaboration with Karolinska University Hospital and the LEO Foundation Skin Immunology Research Center at Copenhagen University. Some authors report engagements with pharmaceutical companies; full details are available in the publication.
Publication
" High-dimensional single-cell analyses reveal neutrophil heterogeneity in guttate psoriasis ", Avinash Padhi, Anoop T. Ambikan, Panagiotis Andriopoulos, Indranil Sinha, Mira Akber, Wenning Zheng, Rokeya Sultana Rekha, Laura Palma Medina, Jan-Inge Henter, Mattias Svensson, , Liv Eidsmo, Anna Norrby-Teglund, Ujjwal Neogi, Peter Bergman, Josefin Lysell , Magda Lourda. eBioMedicine, online 19 February 2026, doi: 10.1016/j.ebiom.2026.106172.
