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Markers of T cell activation include CD69, CD71 and CD25 (also a marker for Treg cells), and HLA-DR (a marker of human T cell activation). CTLA-4 expression is also up-regulated on activated T cells, which in turn outcompetes CD28 for binding to the B7 proteins. This is a checkpoint mechanism to prevent over activation of the T cell.
The activation of T lymphocytes and Natural Killer (NK) cells, both in vivo and in vitro, induces expression of CD69. This molecule, which appears to be the earliest inducible cell surface glycoprotein acquired during lymphoid activation, is involved in lymphocyte proliferation and functions as a signal-transmitting receptor in lymphocytes, including natural killer (NK) cells, and platelets ...
The highest surface expression of this protein is on regulatory T cells (Tregs), where CD25 is expressed constitutively, especially on a subset classified as naturally occurring Tregs. It can also be found on activated B cells, NK (natural killer) cells, thymocytes, and some myeloid lineage cells (e.g. macrophages, dendritic cells).
CD3 (cluster of differentiation 3) is a protein complex and T cell co-receptor that is involved in activating both the cytotoxic T cell (CD8+ naive T cells) and T helper cells (CD4+ naive T cells). [1] It is composed of four distinct chains. In mammals, the complex contains a CD3γ chain, a CD3δ chain, and two CD3ε chains.
In turn, this results in the T cell acquiring an activated phenotype seen by the up-regulation of surface markers CD25 +, CD44 +, CD62L low, CD69 + and may further differentiate into a memory T cell. Having adequate numbers of naive T cells is essential for the immune system to continuously respond to unfamiliar pathogens.
Historically, memory T cells were thought to belong to either the effector or central memory subtypes, each with their own distinguishing set of cell surface markers. [34] Central memory T cells reside in the lymph nodes while effector memory T cells lack the C-C chemokine receptor type 7 (CCR7) and L-selectin (CD62L) receptors, which prevents ...
CD2 is a specific marker for T cells and NK cells, and can therefore be used in immunohistochemistry to identify the presence of such cells in tissue sections. The great majority of T cell lymphomas and leukaemias also express CD2, making it possible to use the presence of the antigen to distinguish these conditions from B cell neoplasms.
Binding to CD28 promotes T cell responses, while binding to CTLA-4 inhibits them. [20] The interaction between CD86 expressed on the surface of an antigen-presenting cell with CD28 on the surface of a mature, naive T-cell, is required for T-cell activation. [21] To become activated, lymphocyte must engage both antigen and costimulatory ligand ...