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Antigen-specific memory T cells specific to viruses or other microbial molecules can be found in both central memory T cells (T CM) and effector memory T cells (T EM) subsets. . Although most information is currently based on observations in the cytotoxic T cells (CD8-positive) subset, similar populations appear to exist for both the helper T cells (CD4-positive) and the cytotoxic T ce
These cells generally reside in the peritoneal cavity. When reintroduced to antigen, some of these B1 cells can differentiate into memory B cells without interacting with a T cell. [4] These B cells produce IgM antibodies to help clear infection. [20] T-bet memory B cells. T-bet B cells are a subset that have been found to express the ...
Central memory T cells also have intermediate to high expression of CD44. This memory subpopulation is commonly found in the lymph nodes and in the peripheral circulation. (Note- CD44 expression is usually used to distinguish murine naive from memory T cells). Effector memory T cells (T EM cells and T EMRA cells) express CD45RO but lack ...
These cells were named central memory T cells (T CM). They effectively stimulate dendritic cells, and after repeated stimulation they are able to differentiate in CCR7- effector memory T cells. Both populations of these memory cells originate from naive T cells and remain in the body for several years after initial immunization. [14]
Additional populations of memory T cells are now known to exist. These include tissue-resident memory T (Trm) cells and virtual memory T cells. [35] The single unifying theme for all memory T cell subtypes is that they are long-lived and can expand quickly to large numbers of effector T cells upon encountering their cognate antigen.
T RM cells develop from circulating effector memory T cell precursors in response to antigen. The main role in formation of T RM cells has CD103 and expression of this integrin is dependent on the cytokine TGF-β. CD8 + effector T cells that lack TGF-β fail to upregulate CD103, and subsequently do not differentiate into T RM cells.
Longitudinal studies on T SCM dynamics in patients undergoing hematopoietic stem cell transplantation (HSCT) have shown that donor-derived T SCM cells were highly enriched early after HSCT, differentiated directly from Tn, and that Tn and T SCM cells (but not central memory or effector T cells) were able to reconstitute the entire heterogeneity of memory T cell subsets including T SCM cells. [6]
Memory B cell activation begins with the detection and binding of their target antigen, which is shared by their parent B cell. [25] Some memory B cells can be activated without T cell help, such as certain virus-specific memory B cells, but others need T cell help. [26]