There has been a long held belief that most of the self-reactive cells in the immune system are removed in the early stages of life. These cells are mostly contained in the thymus. However, new studies contradict the belief. These studies have established that the self-reactive cells can remain in circulation in the human body up to adulthood. The new findings contradict the belief that has been held for more than 25 years. Many specialized cell coordinates in the complex immune system of vertebrates. The coordination is aimed at wiping out developing tumors and foreign invaders. T-cells are some of the cells involved in this critical function. The cells mature in the thymus from which they derive their name.
There are two major varieties of T cells. One of these classes is the killer T cells or cytotoxic T cells, which plays a significant role in attacking and destroying cells containing pathogens such as viruses. The killer T cells also attack most cells that represent any sign of becoming or being cancerous. The proliferation of T cells during the early stages of development cause them to undergo a process of frequent scrambling of the DNA. The scrambling occurs in major parts of their genome resulting in DNA rearrangement. Therefore, a great variance in the types of unfamiliar tissues and pathogens that individual T cells can successfully identify and separate from the community of familiar and healthy tissues. The huge amounts of cell replication leave a high diversity of T cells as far as identification of unfamiliar and pathogen infused cells is concerned. Therefore, a vast array of antigens, which constitute the biochemical component of cancerous cells and pathogens, can be effectively identified for immune detection. Therefore, it is very difficult for cancerous cells and pathogens to invade the human tissues.
As much as the process of random mutation can yield immune cells that can be stimulated by different characteristics of antigens of tumors and pathogens, the process can also produce immune cells that can be activated by countless antigens present in the healthy tissues of a human body. The current theory indicates that this process occurs only among few people late in life creating autoimmune, which indicates that there may be a definite pattern and explanation as to the limited number of its occurrence. Mouse studies have provided much of the theories behind the reason for autoimmune not been experienced by everyone. Scientific research indicated that the frequency of recognition of self-antigens by killer T cells is almost the same as the frequency of recognition of foreign antigens. This indicates that even though the thymus begins shrinking during adolescence and withers into useless fat, there is still a great amount of the cells developed in the thymus that circulate in the body.
Further investigations comparing male and female T cell frequency that can recognize Y-chromosomes indicates that there was about a third as much prevalence of these cells in men as compared to women. The Y chromosome should be self in men and foreign in women. Therefore, T cells detecting Y-chromosomes in women should be a normal scenario. However, the presence of the cells in male indicates that the killer T cells targeting the antigen in men do not disappear completely as a third of them survive.
Stanford University Medical Center. “Adults harbor lots of risky autoreactive immune cells.” ScienceDaily. Science Daily. Web. 19 May 2015. Retrieved from HYPERLINK "http://www.s
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