Navigation Links
Dendritic cells ensure immune tolerance
Date:3/16/2009

One of the most important tasks of the immune system is to identify what is foreign and what is self. If this distinction fails, then the body's own structures will be attacked, the result of which could be an autoimmune disease such as diabetes mellitus type 1 or multiple sclerosis. The only way to protect against these afflictions is to destroy all immune factors that turn against the body's own tissue in other words: immune tolerance. A team working with LMU researcher Dr. David Vhringer has now investigated exactly what role dendritic cells play in this process. There has long been suspicion that these cells, which are important for the body's defenses, are also essential for the establishment and maintenance of immune tolerance. "We investigated mice that lacked this cell type from birth," reports Vhringer. "It turned out that immune cells that attack the body's own tissue survive in these animals, and thereby trigger an autoimmune response. It follows that dendritic cells play a major part in protecting against autoimmune disease."

T cells are a type of white blood cell that are key actors in the body's immune defenses. Each T cell has a receptor on its surface for recognizing just one single antigen. Antigens are molecular structures, mostly fragments of proteins. T cells do not dock onto free antigens, however: they rely on other cells which can present antigens to them. It is the dendritic cells that are primarily responsible for this job. They present the T cells with various antigens, and if an antigen matches a receptor, then that T cell will trigger an immune response from the body.

This is how the body defends itself against pathogens and other intruders. But behind this tactic lies an element of danger to the organism: what happens if the antigen is not foreign, but originates from the body's own tissue instead? A wrongly induced immune response can lead to a severe autoimmune disease that, if left untreated, could lead to destruction of organs or even death. So-called autoreactive T cells, which recognize the body's own structures, must be eradicated or pacified to avoid that they can cause harm. A T cell screening process therefore takes place in the thymus, the bilobular organ in the upper thorax, to distinguish the good from the bad of these dangerous lone mavericks. Each individual T cell is tested, and the autoreactive ones destroyed.

The remaining T cells are checked a second time in the peripheral lymphatic organs of the body. This constant quality control goes on mostly in the lymph nodes and the spleen. As has been known for a while now, dendritic cells can induce peripheral tolerance although it remained unclear whether they are essential for this process. Dendritic cells migrate continuously out of tissues and organs into the lymph nodes, bringing tissue material with them and present it to T cells. Any T cell that reacts to the body's own proteins is then deactivated or killed off.

Most recent findings have shown that dendritic cells are essential to generate and maintain immunological tolerance. "Our work on mice has proven that without dendritic cells, even the first, central screening of autoreactive T cells in the thymus runs only at reduced efficiency," reports Vhringer. "In these animals, the thymus releases T cells that react to the body's own material. These are then activated in the peripheral organs and trigger autoimmunity."

In light of the crucial role these cells play, it is a logical question as to how autoimmunity can be triggered at all without dendritic cells. After all, it is the dendritic cells that undertake certain critical tasks during an immune response. "Among other things, they are specialized in presenting antigens to T cells, which is what makes an immune response at all possible in the first place," says Vhringer. "So we are left with the question as to what type of cell activates the autoreactive T cells if the supposedly most important antigen-presenting cells the dendritic cells are missing. We already have a few candidates for this, and are studying their function more closely now."


'/>"/>

Contact: Luise Dirscherl
dirscherl@lmu.de
49-892-180-2706
Ludwig-Maximilians-Universitt Mnchen
Source:Eurekalert

Related medicine news :

1. Tumors use enzyme to recruit regulatory T-cells and suppress immune response
2. Brain cells work differently than previously thought
3. Embryonic Stem Cells Repair Human Heart
4. Embryonic Human Stem Cells May Help Repair Heart Muscle, Lab Study Shows
5. Circulating fats kill transplanted pancreas cells, study shows
6. Experimental anti-cancer drug made from corn lillies kills brain tumor stem cells
7. Melanoma drug revs immune cells but cancer cells ignore it
8. Scientists explain how insulin secreting cells maintain their glucose sensitivity
9. Embryonic stem cells used to grow cartilage
10. Molecular probe paints cancer cells in living animals, Stanford researchers find
11. USC researcher identifies stem cells in tendons that regenerate tissue in animal model
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/30/2017)... ... April 30, 2017 , ... TransLiquid Cartoon is a ... X. Editors can pick and choose from a variety of liquid transitions that ... shadows using simple color swabs. Utilize on-screen controls to fully manipulate transitions through ...
(Date:4/29/2017)... Aliso Viejo, CA (PRWEB) , ... April 29, 2017 , ... ... effects. Seamlessly transition from one video to the next without having to set ... bleeding, ripping, and blasting transitions to enhance your video production. , TransDark features dynamic ...
(Date:4/28/2017)... ... 2017 , ... An April 24th article on Yahoo! Beauty discusses the case of ... of a weight loss surgery. The woman, declaring “I will not hate my body anymore!” ... her dramatic weight loss. Dr. Feiz & Associates notes that, while it often refers its ...
(Date:4/28/2017)... ... April 28, 2017 , ... Beginning in 2017, Ridgecrest Herbals will ... begins with the popular ClearLungs Extra Strength formula. To ensure that the effectiveness of ... the following ways:, , Removal of the homeopathic element , ...
(Date:4/28/2017)... ... April 28, 2017 , ... ... . These lamps offer an instant energy-saving solution for F32T8 fluorescent lamps on ... or disconnect ballasts. These 50,000 hour rated lamps utilize the existing electronic ballast, ...
Breaking Medicine News(10 mins):
(Date:4/26/2017)... PROVIDENCE, N.J. , April 26, 2017 Phoenix ... announce its fifteenth year of fulfilling its mission of transforming ... industry is highly scrutinized, Phoenix,s innovative ... the healthcare community about the latest advances in science and ... Phoenix was founded in 2002 by ...
(Date:4/20/2017)... , April 20, 2017  Cogentix Medical, ... focused on providing the Urology, Uro/Gyn and Gynecology ... that Ash Keswani has joined the Company as ... this newly created position, Mr. Keswani will report ... CEO. "Our organization is delighted that ...
(Date:4/20/2017)... April 20, 2017 Research and Markets has ... Innovation Driven by Rapidly Expanding Injectables Market and Increasing Usage of ... ... delivery technologies will rise from USD 20 Billion in 2015 to ... Drug Delivery Technologies - Innovation Driven by Rapidly Expanding Injectables Market ...
Breaking Medicine Technology: