Immunoregulatory mechanisms for the hepatitis virus specific T cell response

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In this study, we demonstrated the new concept for the maintenance of memory T cell response. Memory T cells can persist for a long period of time by rejuvenation of T cell memory. Memory CD8+T cells generated during an immune response are long-lived and self-renewing, offering enhanced host protection against re-infection. However, how an antigen- specific population of memory T cells is maintained throughout repetitive infections over potentially a lifetime is not known. Here we investigated the generation and maintenance of antigen- specific CD8+T cells and revealed the new concept that showing dynamic turnover of an antigen-specific memory T cell population during repeated antigen challenge in vivo. We demonstrated that a primary response potentially occurs upon every recall response and find that the skewed T-cell receptor(TCR) repertoire of pre-existing memory T cells is partly corrected by diversity in a newly formed(primary) population. Importantly, memory T cells generated in a more recent antigen encounter expand more vigorously in a subsequent recall response. A primary response during re-challenge therefore restores both the TCR diversity and proliferative potential of the memory T cell population. These findings indicate that memory T cell populations evolve over multiple challenges, favoring memory T cells generated in more recent encounters, and suggest that these primary populations have essential roles in the perpetuation of antigen-specific T cell populations.