Studies have shown that viral antigens persist in the host long after the infection itself is cleared. The mechanisms are unclear, but one suggestion is that low levels of viral transcripts linger in the host. To test this, Li et al. used a model that is independent of genetic information. They transferred naive ovalbumin (OVA)-specific CD8+ T cells to OVA-immunized recipients and found that these cells proliferated in vivo, even 28 days after the initial OVA challenge. However, OVA protein could only be detected in draining lymph nodes for up to 3 days after challenge. Further work showed that dendritic cells (DCs) sequester immunostimulatory epitopes of OVA for as long as 21 days in culture. Treatment of DCs with agents that block heat shock protein 90 (HSP90) abolished their ability to retain immunostimulatory OVA epitopes. So, DCs may promote long-term protective immunity by sequestering pathogen-derived epitopes in an HSP90-dependent manner.