The immune battlefield: The impact of inflammatory cytokines on CD8+ T-cell immunity

Within the microscopic world, there is an ongoing war between the host and foreign invaders, and the battlefield is the immune system. When a pathogen encounters innate immune cells, such as dendritic cells (DCs), it is quickly recognized as foreign. The DCs provide alarm signals in the form of inflammatory cytokines, degrade the pathogen, and present pathogen-derived peptides to adaptive immune cells, including CD8 + T cells. The primary function of CD8 + (or cytotoxic) T cells is to recognize and kill infected cells. They are critical soldiers of the immune system, but before carrying out their function, they must receive 3 signals to become appropriately activated. A nave CD8 + T cell must have T-cell receptor (TCR) engagement by peptide: major histocompatibility complex (MHC) complexes from the antigen-presenting cell (signal 1) [1-5], ligation of costimulatory receptors (signal 2) After integrating the proper signals, the newly activated antigen-specific CD8 + T cells undergo clonal expansion Following clonal expansion, 90%-95% of the pathogen-specific effector CD8 + T-cell population numerically contracts via apoptosis The development of the long-lived memory CD8 + T-cell pool is not a stochastic event, and the cells that seed this population can be identified among effector T cells early following infection. Thus, effector CD8 + T cells can be broadly divided into the following 2 subsets: memory precursor effector cells (MPECs), which will predominantly become long-lived memory CD8 + T cells and short-lived effector cells (SLECs), which are mostly lost during contraction after the T-cell response The establishment of a pool of memory CD8 + T cells is the goal of T-cell vaccination strategies, and understanding how to modulate their function is critical for vaccine development and immunotherapies.