Relevantly, 2 weeks post-infection, while splenic B cells from SV/129 mice retained the basal levels of CD21 expression, the ones from both BALB/c and C57BL/6 mice showed a downregulation of this surface marker, which may indicate a “more immature” B cell compartment (Thorarinsdottir et al., 2015). This evidence concerns the gene CR2 and infection.