Fig 1.
Pathway of conventional and unconventional CD8 T cell memory differentiation.
Naïve CD8 T cells undergoing cognate antigen recognition in the context of an infection or an immunization differentiate into effector cells and form “true” antigen-experienced memory cells or "conventional memory." Under physiological conditions, naïve CD8 T cells may also acquire a memory phenotype in the absence of non-self cognate antigenic stimulation. This may occur in the thymus or in the periphery under the control of cytokines such as IL-4, IL-15, and type I IFN and give rise to “virtual memory” or "innate/memory-like" CD8 T cells.
Fig 2.
Mechanisms of memory CD8 T reactivation and orchestration of protective immune responses.
Upon contact with microbial pathogen, different myeloid subpopulations may rapidly activate memory CD8 T cells through cytokinic and antigenic signals (Phase 1). In turn, memory CD8 T cells produce various cytokines and chemokines (IFNγ, CCL3) that allow initial recruitment and licencing of innate immune cells (Phase 2). Myeloid cells further amplify recruitment (CXCL9/10) of more memory T and innate effectors cells leading to pathogen containement and protective immunity (Phase 3).