IMMUNOLOGY

Detailed explanation-1: -Over the next few days, 90–95% of antigen-specific T cells then die off, leaving behind a pool of memory cells with a range of phenotypes and functionalities. For both CD4 and CD8 T cells, there are two main subclasses of memory cells: central-memory (TCM) and effector-memory (TEM) T cells.

Detailed explanation-2: -Both studies clearly demonstrated that memory T cells are generated from effector T cells through epigenetic modifications, and the studies also revealed that Dnmt3a works as a key DNA methyltransferase affecting memory T cell formation.

Detailed explanation-3: -Activation of peripheral memory T cells. Although the precise mechanisms by which memory T cells mediate protection against these different pathogens have not been formally shown, a common feature of memory T cells at peripheral sites is their ability to rapidly become activated and mediate effector functions (Box 1).

Detailed explanation-4: -Memory T cells are enriched for response to recall antigens. They have a lower activation threshold than naïve T cells, so they are more easily stimulated by antigen in vitro.

Detailed explanation-5: -1. Linear Differentiation Model. The traditional linear differentiation model of T-cell development posits that, upon antigen challenge, naïve CD4 T cells become activated and proliferate into effector cells, which then survive the contraction phase and persist as quiescent memory cells.

Detailed explanation-6: -Abstract. The control of the differentiation pathways followed by responding CD8(+) T cells to produce protective memory cells has been intensely studied. Recent developments have identified heterogeneity at the effector cytotoxic T-lymphocyte level within which a bona fide memory cell precursor has emerged.