CD19 and infection: Furthermore, there was no difference in the total IgG (Fig. 4A) and IgM (Fig. 4B), nor viral-specific IgG (Fig. 4C) and IgM (Fig. 4D) antibody titers between MHV68-infected CD19 Cre-positive and CD19 Cre-negative mice at 16 days post-infection.