Infection-related changes in neutrophil behaviour can trigger psoriasis flares

Photo by Bobjgalindo via Wikimedia Commons

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 in Solna, Sweden. The findings, published in eBioMedicine, suggest how an infection can lead to sudden skin inflammation, particularly in children and young adults.

In the study, the researchers analyzed 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 capable of presenting antigens. 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,” said Avinash Padhi, PhD, in a press release. “Our findings suggest a link between infection and skin inflammation through the accumulation of antigen‑presenting neutrophils in patients’ skin.”

Dr. Padhi is the first author of the study and a Research Specialist at the Department of Medicine, Solna.

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.

They also examined how neutrophils communicate with other cells by analyzing 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, PhD, 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.”

The next phase of the project is to validate the findings in larger, more diverse patient groups, including those 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 drive neutrophil behaviour changes and how neutrophils 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, who coordinated patient recruitment.

The study was conducted in collaboration with Karolinska University Hospital and the LEO Foundation Skin Immunology Research Center at Copenhagen University.