Friday, December 2, 2011

Cells respond to cancer and allergy in similar ways

The cells in our body use similar pathways to protect themselves from cancer and to induce allergy, a new study suggests. When cells are exposed to stress factors that can cause damage leading to cancer, they activate certain stress molecules that call in the help of the immune system. British scientists discovered that these stress molecules also play a role in allergy, when the immune system responds strongly to otherwise harmless particles coming from the environment. Discovering how the body responds to cancer-causing damage is important to develop treatments that involve the immune system.

Cell stress and cancer
When cells come in contact with things that damage them, they send out signals that activate the immune system. Often, it is necessary to clear damaged cells from the body, and that is a job for immune cells that become activated after stress signals have been given out. It was already known that this mechanism exists, but how the body regulates this response was previously unknown. British scientists discovered that distressed cells signal to cell-killing immune cells by activating a receptor called NKG2D. T cells, highly specialized in killing, are then able to clear the damaged cells, thus protect the body against cancer. 

Activating an allergic response
The same receptor can also be found on other immune cells, those responsible for launching an attack that is found during allergy, where the body responds with molecules called antibodies that bind to a certain foreign molecule to neutralize them. It is interesting to note that two distinct forms of pathology have common grounds. However, in cancer, activation of NKG2D is important to combat the disease, while allergy is something best shut down, which would imply inhibition of NKG2D.

Developing medicine
The newly discovered mechanism is relevant for the development of immune based therapy. Because the immune system already plays a role in preventing cancer, we can improve it to do a better job when cancer seems to be on the winning hand. Improving the activation of NKG2D by drugs could prove to be beneficial in preventing cancer, or to help the immune system kill cancer cells when they have progressed and are already able to escape from the immune system. Naturally, after discovering its dual role in allergy, it is likely to assume that drugs developed based on this mechanism could have side effects that include an allergic reaction. This calls for more research to find out how to make this a therapy that targets cancer only.

Activating the immune system
Ordinary cells have specialized receptors which they use to activate the immune system. The so called major histocompatibility complex (MHC) is used to 'present' viral or bacterial particles to immune cells to give a sign of infection. Immune cells, especially T cells are trained to recognize MHC receptors and consequently become activated. They generate a response against molecules found on MHC, which shows how the body can generate a specific response that focuses on attacking a single surface marker, that can be part of a pathogen which is consequently killed. Cells constantly process intracellular proteins and present parts of them to immune cells. However, only in the case of foreign molecules is the immune system activated. This is because the immune system has learned to distinguish foreign from body-own molecules, prior to being released to the circulation.

Immune based therapy is only one of many initiatives being developed to combat cancer. Other ideas include using viruses to kill cancer cells, or using new techniques such as nanoparticles. Sometimes, scientists get very creative, such as with the development of a protein switch that kills a cancer cell from within. In addition, existing drugs get screened for potential as anti-cancer drug, such as aspirin.

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