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In immunology, a naive T cell (T h 0 cell) is a T cell that has differentiated in the thymus, and successfully undergone the positive and negative processes of central selection in the thymus. Among these are the naive forms of helper T cells ( CD4 + ) and cytotoxic T cells ( CD8 + ).
V(D)J recombination (variable–diversity–joining rearrangement) is the mechanism of somatic recombination that occurs only in developing lymphocytes during the early stages of T and B cell maturation. It results in the highly diverse repertoire of antibodies/immunoglobulins and T cell receptors (TCRs) found in B cells and T cells, respectively.
Priming of naive CD8 T cells generates cytotoxic T cells capable of directly killing pathogen-infected cells. CD4 cells develop into a diverse array of effector cell types depending on the nature of the signals they receive during priming. CD4 effector activity can include cytotoxicity, but more frequently it involves the secretion of a set of ...
Quiescence can prevent naive T cell activation after tonic signaling, meaning that T cells may be constitutively activated when not in the presence of a ligand. [21] After antigen exposure and costimulation, naive T cells start the process called quiescence exit, which results in proliferation and effector differentiation. [22]
The antigen sensitivity is higher in antigen-experienced T cells than in naive T cells. Naive T cells pass through the process of functional avidity maturation with no change in affinity. It is based on the fact that effector and memory (antigen-experienced) T cell are less dependent on costimulatory signals and higher antigen concentration ...
CD2 was shown to prime naive T cells (T N) even without CD28 or TCR. [2] Also, CD27 is a receptor constitutively expressed on T N (its expression is downregulated upon TCR stimulation) and enhances T cell proliferation. [9] The differentiation of T helper cells (T H) into different subsets also partially depends on their co-stimulatory molecules.
The remaining cells exit the thymus as mature naive T cells, also known as recent thymic emigrants. [13] This process is an important component of central tolerance and serves to prevent the formation of self-reactive T cells that are capable of inducing autoimmune diseases in the host.
T cells' functional capacity is most influenced by aging effects. Age-related alterations are evident in all T-cell development stages, making them a significant factor in immunosenescence. [27] T-cell function decline begins with the progressive involution of the thymus, which is the organ essential