The Molecule that Fights Psoriasis

By Sondra Forsyth

Researchers have discovered how IL-4 can fight psoriasis on a molecular level.

Scientists have known that Interleukin 4, also known as IL-4, an endogenous signal molecule, inhibits the inflammation that is characteristic of psoriasis. But until now, it wasn’t clear exactly how that happened.

Inflammation defends the body against invaders. But sometimes poorly directed immune reactions can trigger inflammation even though there is no attack from outside. That can cause tissue damage in psoriasis, and is a factor in other autoimmune disease such as multiple sclerosis and rheumatoid arthritis.

Researchers from the Technische Universität München (TUM) and the University of Tübingen used an animal model and a study of patients to increase the understanding of how IL-4 plays an important role in the immune system.

“Together with colleagues from Tübingen, we were able to show in earlier studies that the signaling molecule IL-4 is a promising candidate for the treatment of psoriasis,” said Prof. Tilo Biedermann, who holds the chair for Dermatology and Allergology and is Director of the Clinic and Polyclinic for Dermatology and Allergology. “However, before IL-4 can be used as a standardized medication, we have to understand the exact mechanism of action – and we’ve now succeeded in doing just that.”

In the study, according to a news release from TUM,  the scientists discovered that IL-4 inhibits specific immune cells in a natural way: it prevents the cells from synthesizing and releasing two signaling molecules, known as IL-23 and IL-17.

“The discovery is very interesting in that IL-23 activates special T-cells in the body, thus triggering inflammation. Evidently IL-4 is able to effectively block this pathway,” says Biedermann. In subsequent experiments with mice, the scientists also found that administration of IL-4 specifically inhibits inflammation of the skin via this mechanism.

Twenty-two patients with psoriasis were given injections of IL-4 over a period of six weeks Before treatment with IL-4, the study participants had high levels of IL-23 and IL-17 in their inflamed and itchy skin. After successful treatment, the two substances were barely detectable, and  inflammation and psoriatic skin changes disappeared.

The findings were published in the Proceedings of the National Academy of Sciences.