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

<p>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.