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Memory T cells are a subset of infection- as well as potentially cancer-fighting T cells (also known as a T lymphocyte) that have previously encountered and responded to their cognate antigen; thus, the term antigen-experienced T cell is often applied. Such T cells can recognize foreign invaders, such as bacteria or viruses, as well as cancer cells. Memory T cells have become "experienced" by having encountered antigen during a prior infection, encounter with cancer, or previous vaccination. At a second encounter with the invader, memory T cells can reproduce to mount a faster and stronger immune response than the first time the immune system responded to the invader. This behaviour is utilized in T lymphocyte proliferation assays, which can reveal exposure to specific antigens. ==Sub-populations== Within the overall memory T cell population, at least three distinct subpopulations have been described and can be recognised by the differential expression of chemokine receptor CCR7 and L-selectin (CD62L). * ''Stem memory'' TSCM cells, like naive cells, are CD45RO−, CCR7+, CD45RA+, CD62L+ (L-selectin), CD27+, CD28+ and IL-7Rα+, but they also express large amounts of CD95, IL-2Rβ, CXCR3, and LFA-1, and show numerous functional attributes distinctive of memory cells. * ''Central memory'' TCM cells express L-selectin and the CCR7, they secrete IL-2, but not IFNγ or IL-4. * ''Effector memory'' TEM cells, however, do not express L-selectin or CCR7 but produce effector cytokines like IFNγ and IL-4. More recently, other sub-populations have been explored using co-stimulatory molecules CD27 and CD28 expression in addition to CCR7 and CD62L. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Memory T cell」の詳細全文を読む スポンサード リンク
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