Thursday, March 22, 2012

New breed of cells could treat autoimmune diseases

When a patient's immune system attacks its own tissues or cells, he or she suffers from an autoimmune disease. Normally, the immune system only attacks things that are foreign to our body, such as microbes and viruses. However, if something goes wrong during the development phase in early life, it is possible that some immune cells do not recognize tissues as body-own. Such is the case in diabetes type 1, in which insulin-producing cells are destroyed because our defensive systems think the tissues are foreign and need to be destroyed. In these cases, and in other situations where the immune response is too heavy, we need something that calms our defence mechanisms down. Scientists from Cardiff University may have found just the thing we need, and they found it by scraping cells of people's cheeks.

Our immune system consists of a wide variety of cells. By connecting to each other and sending out signals, an immune response is being build up, ready to strike after something foreign has been recognized. When a microbe enters the body, specialized 'snatchers' recognize them and present their findings, in the form of small molecular parts called antigens, to more specialized cells. These so-called antigen-presenting cells induce signals that allow for building an army of, mostly, lymphocytes tasked with destroying the incoming threat. However, there are also cells that are able to calm the lymphocytes down and inhibit an immune response. Cells with these capabilities have, perhaps surprisingly, been harvested from the cheek by Cardiff scientists.
Cheek cells appearing to be powerful enough to stop lymphocytes from attacking cells and tissues were obtained from one of the upper layers of the cheek's cellular lining. To be precise, they are called oral mucosal lamina propria progenitor cells. Originally, they were derived from a primitive group of cells destined to form neurons, the cells of the neural network. OMLP-PCs, as they are known, also have the capability to differentiate into neural cells, which makes it all the more surprising that they have immunosuppressive potency. After scraping them off the cellular lining of the cheek, scientists found a way to culture OMLP-PCs in the lab and study their characteristics.

Even more striking than their origin, is the way OMLP-PCs stop the immune system's lymphocytes from destroying whatever it is they set their sights on. Cheek cells inhibit lymphocytes without actually 'touching' them, as is customary for cellular interaction in the immune system. Additionally, the effect of OMLP-PCs is dose-independent, which means application of a high load of cheek cells is unnecessary for the required effect. Even in small doses, scientists noted full inhibition of lymphocytes. It is quite surprising that a small number of cells coming from the cheek are so effective in restraining an immune response.

After examining the cheek cells more carefully, we may be able to use them in a therapeutic setting. Administering cheek cells to patients suffering from an autoimmune disease such as diabetes type 1, multiple sclerosis or rheumatoid arthritis might alleviate their symptoms by inhibiting the cells causing the problem. Equally important is subduing of the immune system in patients undergoing organ transplantation. Even though we are all human, tissues from other people do not belong in your body as far as your immune system is concerned. This also calls the need for immunosuppression. One of the downsides is the fact that it leaves you exposed to real threats: pathogens such as bacteria or viruses will find it easier to make your body their home when your defence system is down.
A greatly simplified illustration of the variety of cells in the immune system. In reality, the number of cells and their function is much more complex. It does show the different groups of lymphocytes. Tc cells are used for killing, while Th cells have a supportive role. B cells, or plasma cells, make antibodies: small molecules that bind and neutralize pathogens. Memory cells remember what happened during a foreign invasion and make an immune response much more effective if the pathogen invades a second time. Vaccination is based on the function of memory cells.

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