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Reactive lymphocytes are usually associated with viral illnesses, but they can also be present as a result of drug reactions (such as phenytoin), immunizations, radiation, and hormonal causes (such as stress and Addison's disease), as well as some autoimmune disorders (such as rheumatoid arthritis). [7] Some pathogen-related causes include: [6]
EBV-positive reactive lymphoid hyperplasia (or EBV-positive reactive lymphoid proliferation) is a benign form of lymphadenopathy, i.e. swollen, often painful lymph nodes. The disorder is based on histologic findings that occur in the lymphoid tissue of mainly older individuals who were infected with EBV many years earlier.
Lymphocytosis is a feature of infection, particularly in children. In the elderly, lymphoproliferative disorders, including chronic lymphocytic leukemia and lymphomas, often present with lymphadenopathy and a lymphocytosis. [citation needed] Causes of absolute lymphocytosis include:
Lymph nodes help filter these fluids by removing material towards the direction of blood circulation. When antigens are presented, the lymphocytes inside of the node trigger a response which can cause proliferation or cell enlargement. This is also referred to as reactive lymphadenopathy. [8]
Lymphoproliferative disorders are a set of disorders characterized by the abnormal proliferation of lymphocytes into a monoclonal lymphocytosis. The two major types of lymphocytes are B cells and T cells , which are derived from pluripotent hematopoietic stem cells in the bone marrow .
A viral infection can directly cause encephalitis or trigger a cascade ending in autoimmunity, with both mechanisms eventually leading to a rise in CSF lymphocyte concentration. [ citation needed ] For patients with Herpes simplex virus , more than 90% are found to have lymphocytic pleocytosis of varying levels. [ 5 ]
In immunology, central tolerance (also known as negative selection) is the process of eliminating any developing T or B lymphocytes that are autoreactive, i.e. reactive to the body itself. [1] Through elimination of autoreactive lymphocytes, tolerance ensures that the immune system does not attack self peptides. [2]
A lymph node is small, capsulated lymphoid organ that is present along the lymphatic system. It is composed of cortex and medulla. The cortex is also divided into outer cortex and inner cortex (also known as the paracortex).