A key component in the immune system is a group of cells called white blood cells, which help defend the body against foreign invaders and microorganisms. One type of white blood cell that is believed to be of crucial importance in causing psoriasis is the T-lymphocyte.
The T-lymphocytes are very smart cells because they have terrific memories. In fact, once they are exposed to a foreign substance, they remember it forever. With subsequent exposures, the T-lymphocytes will recognize the substance and multiply to attack it. Hence, they are known as memory T-cells.
While T-cells have great memories for foreign substances, they need a teacher. That teacher is known as an antigen presenting cell (APC), which does exactly what its name says: It presents antigen (foreign substances) to the T-cell and teaches the T-cell about the antigen. The T-cell, with its fantastic memory, will then remember that foreign substance in future encounters. T-cells naturally circulate throughout the body looking for antigens. The presence of the antigen, usually an outside invader, such as a virus or bacteria, activates the T-cell, which then initiates an immune response to neutralize the antigen.
In psoriasis, activated T-cells accumulate in the outer layer (epidermis) and inner layer (dermis) of the skin, where they reproduce at a rapid rate due to chemicals called cytokine, such as tumor necrosis factor-alpha (TNF-alpha), which sends a faulty message to the skin, causing the skin cells to grow and divide more rapidly and resulting in the thick, scaly skin of psoriasis. The reason this happens and the exact process continue to be the focus of intense scientific interest and research. It is becoming increasingly clear that certain interleukins, interleukin-23 (IL-23) and interleukin-22 (IL-22), and new types of recently described T-cell (T-helper 17) are of central importance in the development of psoriasis.
lnterleukin-12, interleukin-22, and interleukin-23 are recognized as important chemical messengers in the cause of psoriasis. These chemicals, or cytokines, have been shown to induce the changes in the skin that are consistent with psoriasis, both in animals and human experiments.
Researchers in the mid-1990s proved that T-cells in the skin release specific cytokines (proteins) that are capable of causing skin cells to grow. Researchers are still carefully examining the process to determine the specific antigen that activates the immune system and fuels the entire process - the so-called key to psoriasis.
Taken together, this summarizes our current understanding of the immune mechanisms causing psoriasis. This has taken scientists more than twenty years to understand. These understandings have provided important insight into permitting the development of new medicines to treat these immune defects and improve psoriasis.
Who Is Most at Risk?
Psoriasis is most commonly diagnosed between the ages of 15 and 35, but it can occur at birth or, less often, in the elderly. The average age of onset in males is 29, and in females, 27. A second peak can occur in the mid-50s. About 10-15 percent of all cases occur in children under the age of 10. Men and women are affected equally. Although anyone can develop psoriasis, the incidences are much lower in West Africans, African Americans, Japanese, Inuit, and Native Americans, a fact that led researchers to believe the cause of psoriasis might involve genetic and environmental factors or triggers.
Genetics
A family history of psoriasis has long been known as a risk factor for developing this disease. Approximately one-third of patients have a family history of psoriasis. If a first-degree relative has psoriasis, such as a sibling or parent, then there is a 10-20 percent chance of the child developing psoriasis as well. If both parents have psoriasis, the risk of their child developing psoriasis is 50 percent. These statistics strongly suggest that genes or genetics play an important and central role in causing psoriasis.
A gene is a part of the DNA (deoxyribonucleic acid) that contains information you inherit. This information includes the color of your hair and eyes, and whether you are susceptible to certain diseases. Researchers are still uncertain which specific genes are involved or exactly how the environment plays a role in triggering psoriasis. In fact, it may be that several genes are required to cause psoriasis.
One of the strongest indications that psoriasis has a genetic basis comes from studies of identical twins. Identical twins have all the same genes. Fraternal twins, however, share only some of the same genes. In identical twins, chances are three times greater that psoriasis will be present in both siblings, compared to fraternal twins. Even if multiple genes are required to cause psoriasis, this finding is important in indicating a genetic basis. To find out more, you can check out Psoriasis Immune System.