The B cell chemoattractant, CXCL13 was dramatically lower in aged as compared to juvenile animals, regardless of infection status whereas CXCL12 and CCL20, known dendritic cell (DC) chemoattractants, were much higher in mock and SARS-CoV infected aged animals (Figure 4D-F; unpaired student T-test). This evidence concerns the gene CXCL13 and infection.