Stimulation of naïve and memory T cells by cytokines.
On the basis of cell surface markers, mature T cells are considered to have either a naïve or a memory phenotype. These cells exhibit distinct types of kinetic behaviour in vivo. While naïve-phenotype cells persist long term in a non-dividing state, memory-phenotype T cells include cycling cells and exhibit a more rapid rate of turnover; this has also been shown to be true for cells that can be definitively identified as naïve or memory T cells respectively. The number of memory-phenotype (CD44hi) CD8+ T cells entering cell cycle is greatly increased after in vivo exposure to viruses, bacteria or components of bacteria. Accelerated turnover of memory T cells also occurs after the injection of a variety cytokines that are induced by infectious agents, including type I interferon (IFN-I). Although naïve-phenotype T cells do not divide in response to these cytokines, they do exhibit signs of activation, including upregulation of CD69 after exposure to IFN-I. These findings suggest that the dissimilar in vivo kinetics of naïve- and memory-phenotype T cells might reflect their divergent responses to cytokines. Furthermore, the ability of infection-induced cytokines to stimulate non-specific proliferation of memory-phenotype T cells and partial activation of naïve-phenotype T cells implies that they play a complex role during primary immune responses to infectious agents.
Tough
D F
DF
Edward Jenner Institute for Vaccine Research, Compton, Newbury, Berkshire, England. david.tough@jenner.ac.uk
Sun
S
S
Zhang
X
X
Sprent
J
J
D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000818:Animals; D016207:Cytokines / Q000494:pharmacology*; D006801:Humans; D007156:Immunologic Memory; D007370:Interferon Type I / Q000494:pharmacology; D008285:Major Histocompatibility Complex; D011994:Recombinant Proteins; D013601:T-Lymphocytes / Q000276:immunology*
D000276:Adjuvants, Immunologic; D016207:Cytokines; D007370:Interferon Type I; D011994:Recombinant Proteins