3d illustration of a cross-section of a diseased skin with melanoma that enters the bloodstream and lymphatic tract
Credit: Christoph Burgstedt/Getty Images

Researchers at Karolinska Institutet in Sweden and the University of Copenhagen in Denmark have demonstrated how memory killer cells are formed in the skin and have shown how high levels of these cells in cancer tissue correlate with longer survival rates in people with melanoma.

This particular from of T cell, which are called tissue-resident memory cells are formed in the skin and other tissue protect against infections that they have encountered previously. Some of these cells, called memory killer cells, express proteins that allow them to kill infected cells. These cells also can contribute to skin disorders like vitiligo and psoriasis. They have also been shown to be involved in the immune response to certain forms of cancer and have shown they can be activated by immunotherapy.

“We don’t know so much about how and why memory killer cells are formed in the skin and what it means for cancer patients,” said Prof. Yenan Bryceson at the Department of Medicine (Huddinge), Karolinska Institutet. “Finding out how these cells develop enables us to contribute to the development of more efficacious immunotherapy for diseases like melanoma.”

The study, published in the journal Immunity, was a collaborative effort between researchers at Karolinksa Institutet Beatrice Zitti and Elena Hoffer. To chart the development of memory killer cells in human skin, the pair isolated T cells from the skin and blood of healthy volunteers and used advanced techniques to examine gene activity and expression of different proteins. This allowed them to identify T cells in the blood with the potential to develop into memory killer cells in skin or other tissues. After knocking out specific genes, they could also demonstrate which genes are required for the maturation of memory killer cells in tissue.

The team then moved to the study of tumor samples of melanoma patient and discovered that patients with longer survival rates also had a higher accumulation of epidermal memory killer cells. Using the information, the researchers hope to discover ways to optimize immunotherapy approaches that will improve T cell response.

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