In addition, lymphomas may develop when defective lymphocytes are not properly destroyed by apoptosis.
The loss of functional SAP disrupts proper signaling in the immune system and may prevent the body from controlling the immune reaction to EBV infection. Others result in an abnormally short protein that is unstable or nonfunctional, or prevent any SAP from being produced. Some SH2D1A gene mutations impair SAP function. The SAP protein also helps control immune reactions by triggering self-destruction ( apoptosis ) of cytotoxic lymphocytes when they are no longer needed. This protein is involved in the functioning of lymphocytes that destroy other cells (cytotoxic lymphocytes) and is necessary for the development of specialized T cells called natural killer T cells. The SH2D1A gene provides instructions for making a protein called signaling lymphocyte activation molecule (SLAM) associated protein (SAP). SH2D1A gene mutations cause XLP1, and XIAP gene mutations cause XLP2. Mutations in the SH2D1A and XIAP genes cause XLP. Some researchers believe that these individuals should actually be considered to have a similar but separate disorder rather than a type of XLP. People with XLP2 have not been known to develop lymphoma, are more likely to develop hemophagocytic lymphohistiocytosis without EBV infection, usually have an enlarged spleen (splenomegaly), and may also have inflammation of the large intestine (colitis). XLP can be divided into two types based on its genetic cause and pattern of signs and symptoms: XLP1 (also known as classic XLP) and XLP2. Death usually results from hemophagocytic lymphohistiocytosis. Without treatment, most people with XLP survive only into childhood. Individuals with dysgammaglobulinemia are prone to recurrent infections.Ĭancers of immune system cells ( lymphomas ) occur in about one-third of people with XLP. Antibodies (also known as immunoglobulins) are proteins that attach to specific foreign particles and germs, marking them for destruction. In some individuals with XLP, hemophagocytic lymphohistiocytosis or related symptoms may occur without EBV infection.Ībout one-third of people with XLP experience dysgammaglobulinemia, which means they have abnormal levels of some types of antibodies. The spleen, heart, kidneys, and other organs and tissues may also be affected. Hemophagocytic lymphohistiocytosis causes fever, destroys blood-producing cells in the bone marrow, and damages the liver. This proliferation of immune cells often causes a life-threatening reaction called hemophagocytic lymphohistiocytosis. People with XLP may respond to EBV infection by producing abnormally large numbers of T cells, B cells, and other lymphocytes called macrophages. However, the virus is generally inactive (latent) because it is controlled by other lymphocytes called T cells that specifically target EBV-infected B cells.
Normally, after initial infection, EBV remains in certain immune system cells (lymphocytes) called B cells.
In some people it causes infectious mononucleosis (commonly known as "mono"). EBV is a very common virus that eventually infects most humans. More than half of individuals with this disorder experience an exaggerated immune response to the Epstein-Barr virus (EBV). X-linked lymphoproliferative disease (XLP) is a disorder of the immune system and blood-forming cells that is found almost exclusively in males.
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