Killer T cells regulate antigen presentation for early expansion of memory, but not naive, CD8+T cell

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Abstract
Antigen presentation within the lymph node draining a site of infection is crucial for initiation of cytotoxic T cell responses. Precisely how this antigen presentation regulates T cell expansionin vivois unclear. Here, we show that, in primary infection, antigen presentation peaks ≈3 days postinfection and then slowly decays until day 12. This prolonged antigen presentation is required for optimal expansion of naive CD8+T cells, because early ablation of dendritic cells reduces the later CD8+T cell response. Antigen presentation during secondary infection was 10-fold lower in magnitude and largely terminated by day 4 postinfection. Expansion of memory, but not naive, antigen-specific T cells was tightly controlled by perforin-dependent cytolysis of antigen-presenting cells. The ability of the memory T cells to remove antigen-presenting cells provides a negative-feedback loop to directly limit the duration of antigen presentationin vivo.