IL21R+/+/IL21R-/- mixed bone marrow chimeric mice were infected intranasally with 1,000 pfu of MHV68-H2bYFP and spleens were harvested at the indicated days. (A) Total number of Ly5.1+ IL21R+/+ and Ly5.2+ Il21R-/- splenocytes harvested. (B) Percentage of B cells with a germinal center phenotype. Cells were gated on Ly5.1+ or Ly5.2+, B220+ CD3-, CD4-, CD8- and germinal center B cells were defined as CD95hi GL7hi. (C) Percentage of splenocytes with a plasma cell phenotype. Cells were gated on CD3-, CD4-, CD8- and plasma cells were defined as B220neg-lo CD138hi. (D) Percentage of splenocytes that were MHV68 infected (YFP+). Cells were gated on CD3-, CD4-, CD8- splenocytes. **, p = 0.0029; ****,p<0.0001.