Secondary memory CD8+ T cells are more protective but slower to acquire a central-memory phenotype.
The formation of memory CD8 T cells is an important goal of vaccination. However, although widespread use of booster immunizations in humans generates secondary and tertiary CD8 T cell memory, experimental data are limited to primary CD8 T cell memory. Here, we show that, compared with primary memory CD8 T cells, secondary memory CD8 T cells exhibit substantially delayed conversion to a central-memory phenotype, as determined by CD62L expression and interleukin (IL)-2 production. This delayed conversion to a central-memory phenotype correlates with reduced basal proliferation and responsiveness to IL-15, although in vitro coculture with a high concentration of IL-15 is capable of inducing proliferation and CD62L upregulation. Functionally, secondary memory CD8 T cells are more protective in vivo on a per cell basis, and this may be explained by sustained lytic ability. Additionally, secondary memory CD8 T cells are more permissive than primary memory CD8 T cells for new T cell priming in lymph nodes, possibly suggesting a mechanism of replacement for memory T cells. Thus, primary and secondary memory CD8 T cells are functionally distinct, and the number of encounters with antigen influences memory CD8 T cell function.
Jabbari
Ali
A
Interdisciplinary Graduate Program in Immunology, University of Iowa, Iowa City, IA 52242, USA.
Harty
John T
JT
D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000145:classification* / Q000166:cytology / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology*; D002478:Cells, Cultured; D018920:Coculture Techniques; D007156:Immunologic Memory; D016130:Immunophenotyping; D019041:L-Selectin / Q000096:biosynthesis / Q000235:genetics; D008089:Listeria monocytogenes / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D016176:T-Lymphocyte Subsets / Q000145:classification / Q000166:cytology / Q000276:immunology
D019041:L-Selectin