Definition of transient ischemic attack. : a brief episode of cerebral ischemia that is usually characterized by temporary blurring of vision, slurring of speech, numbness, paralysis, or syncope and is often predictive of a serious stroke âabbreviation TIA âcalled also ministroke.
Germinal centers are an important part of the B cell humoral immune response, acting as central factories for the generation of affinity matured B cells specialized in producing improved antibodies that effectively recognize infectious agents, and for the production of durable memory B cells.nce these B cells have stopped proliferating, they migrate to the light zone where they are known as centrocytes, and are subjected to selection by follicular helper T (TFH) cells in the presence of follicular dendritic cells (FDCs).
About.com states that lymph nodes are found in each part of the body except for the central nervous system. The lymph filtered by these specialized tissues refers to the clear fluid that surrounds the cells. According to About.com, the lymph nodes have an important function of filtering the lymph of pathogens, such as bacteria and viruses, dead cells, wastes and cancerous cells. The lymph that is filtered is then returned to the blood to prevent edema or the excess fluid buildup in the tissues. About.com also explains that lymph nodes contain lymphocytes, which are immune system cells that are responsible for identifying and battling pathogens.