Fig 3. IL-21 signaling is required for efficient viral reactivation from splenocytes.

To determine the frequency of splenocytes capable of reactivating virus, limiting dilution analysis was performed on splenocytes from mice infected intranasally with 1,000 pfu of MHV68-H2bYFP and harvested at days (A) 14, (B) 16, (C) 18 and (D) 20 post-infection. Serial dilutions of splenocytes were plated on MEFs and the percentage of wells positive for cytopathic effect (CPE) was determined 14 days post-plating. Mechanically disrupted splenocytes were plated in parallel to detect the presence of preformed infectious virus. Results are from 3 independent experiments at each time point with 3–6 mice per group.