autophagy ... is important for differentiation into memory T cells
Autophagy has previously been reported to be more active in proliferating T cells than resting T cells; however, these studies were done in vitro in T cells that developed in the absence of autophagy-related protein 5 (ATG5) and ATG7. Thus, Xu et al. used phenotypically normal naive CD8+ T cells to study the role of autophagy during CD8+ T cell activation in response to lymphocytic choriomeningitis virus (LCMV) in vivo. The authors isolated virus-specific CD8+ T cells at distinct stages of the T cell response to LCMV infection: the T cell expansion phase at day 5 after infection, the peak of T cell expansion at day 8, the T cell contraction phase at day 15 and the memory phase at day 30. The authors did a series of careful experiments to assess autophagy activity, including determining the levels of the autophagy-related protein LC3B and generating a reporter system with recombinant LC3B protein fused to green fluorescent protein. They showed that autophagy was diminished in LCMV-specific CD8+ T cells during the clonal expansion phase at day 5, but then rapidly increased during the transition into the memory phase. Hence, autophagy seems to be inhibited during CD8+ T cell clonal expansion, but is important for differentiation into memory T cells.
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