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Researchers: Natural killer cells show an immunological memory

Researchers: Natural killer cells show an immunological memory


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New therapy options based on natural killer cells
The activation of natural killer cells could play an outstanding role in the future, particularly in the treatment of cancer. In a recent study, scientists from the Ludwig Maximilians University (LMU) in Munich and the University of Bonn have now deciphered a special autoimmune mechanism in the skin and have proven "that the so-called natural killer cells also have an immunological memory for the body's own cells."

The research team led by Professor Veit Hornung from the LMU has succeeded in deciphering the mechanism by which the immune system can attack pigment cells in the skin, the LMU announced. In addition, the scientists found that - contrary to the previous assumption - natural killer cells have a kind of memory. The researchers published the results of their study in the specialist magazine "Immunity".

Natural killer cells can "remember" tissue
So far, “natural killer cells have been denied that they have an immunological memory for the body's own tissue,” reports the LMU. In the current study, it has now been proven that these immune cells “remember” the pigment cells when they come into frequent contact with a specific contact allergen. An effect that can possibly also be used for therapeutic purposes. For example, the natural killer cells could also be used to prevent and treat black skin cancer.

Immune system attacks pigment cells of the skin
The skin's pigment cells form an indispensable protective shield against UV radiation. Its effect is also evident in the popular summer tan, which can only be formed by the pigment cell enzyme tyrosinase. "The more the sun burns from the sky, the more pigments are formed by this enzyme," reports the LMU. The enzyme monobenzone can block this enzyme and thus trigger a stress reaction. In this case, the immune system then attacks the affected pigment cells. A common consequence of this is the "white spot disease" (Vitiligo), which leads to pigment-free areas on the skin.

Vitiligo can be used against skin cancer?
Earlier scientific studies have shown that people with vitiligo have a lower risk of developing dreaded black skin cancer, the researchers explain. The active triggering of the disease by the tyrosinase blocker monobenzone could be a possible way to treat this type of cancer. "So you want to use a less serious illness as a weapon against black skin cancer," explains Dr. Jasper van den Boorn from the Institute for Clinical Chemistry and Clinical Pharmacology at the University of Bonn. To make this possible, however, the researchers first had to understand the mechanism by which the immune system recognizes and attacks the pigment cells exposed to monobenzone as dangerous.

Special hapten mobilizes the natural killer cells
It was known that monobenzone has a contact-sensitizing effect on pigmented skin. The substance alone does not trigger any reaction on the skin, but "only when the monobenzone docks to the tyrosinase does it create a hapten in the pigment cell, a foreign structure that can activate the immune system," reports the LMU. In the animal model, the researchers examined how the immune defense reacts to this hapten. The result was surprising. "Normally, the immune system mobilizes a mixture of different white blood cells to attack a tissue exposed to hapten," but "multiple exposure to monobenzones only caused the natural killer cells to attack pigment cells," explains Jasper van den Boorn.

Effective immune response against black skin cancer
As part of the immune system, natural killer cells kill abnormal cells such as cancer cells or virus-infected cells. So far, doctors have assumed that they do not have an immunological memory for the body's own tissue, as is attributed to T and B lymphocytes, for example. "However, our results clearly show that the natural killer cells can also bring about a sustainable and effective immune response against the body's own pigment cells and thus also against black skin cancer cells," emphasizes the director of the Institute for Clinical Chemistry and Clinical Pharmacology at the University of Bonn, Professor Dr. Gunther Hartmann.

To initiate the corresponding immune response, according to the LMU, "only one control point had to give the green light: the NLRP3 inflammasome." This was a "protein complex that, like a central point, brings together multiple signal information and acts as a switch to decide whether immune cells and the natural killer cells receive the marching order, ”explains Prof. Hornung. If this "checkpoint" was put out of action, the desired immune response was not triggered by the monobenzone tyrosinase hapten. (fp)

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