How to monitor the immune system
The immune system consists of cells of various types distributed throughout the body and ready to fight at the first sign of infection. Monitoring the localization of immune reactions in various pathologies, as well as the effect of various drugs on the immune system, would make it easier for clinicians to diagnose and treat a large number of diseases. However, until now, there has been no method of visualizing immune reactions in the body.
Scientists at the University of California (Los Angeles), working under the guidance of Dr. Owen Witte, have developed a contrast agent for positron emission tomography, which allows you to track the immune response in the body during the development of many diseases, including oncological and infectious.
The aim of the authors was not to observe specific immune cells, but the immune response as a whole. To do this, they created a marker that allows us to assess the activity of a biological process characteristic of most immune cells.
The process chosen by scientists – DNA processing – provides fast and efficient division of immune cells. Most cells of the body, when dividing, slowly synthesize the structural elements of the daughter cell from the nutrients entering the body. However, in the presence of infection, immune cells should divide as quickly as possible. To do this, they process the free nucleotides contained in the body – DNA fragments formed during the destruction of dead cells or ingested with food. The new marker binds to an enzyme necessary for the normal course of the first stage of DNA processing in immune cells.
The authors conducted a large-scale screening of existing drugs and selected the chemotherapy drug gemcitabine, which effectively penetrates into immune cells. They modified the molecular structure of the drug and obtained a compound that passes unhindered through the cell membrane, and in the presence of the desired enzyme is phosphorylated and loses mobility. The researchers attached a radioactive tag to the marker molecules, which glows during positron emission tomography.
The effectiveness of the new marker was tested on mice that were previously injected with a virus that causes the formation of immunogenic tumors. The introduction of a new probe to such mice and subsequent positron emission tomography made it possible to obtain three-dimensional images resembling temperature maps, on which a large number of immune cells are indicated in red, moderate in green, and low in red. For example, the lymph nodes located in the immediate vicinity of the tumor look especially bright.
The authors believe that in the future, doctors will be able to use a new probe to visualize immune responses. In combination with other methods, such as computed tomography, it will allow you to observe a decrease in the size of the tumor during treatment.
The disadvantage of the method is not absolute specificity, and scientists are already conducting a systematic analysis of chemical compounds in the hope of developing more sensitive and specific to certain types of immune cells probes.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of TechnologyReview
10.06.2008