CD8A and infection: However, in contrast to CD8+ T cells, the number of splenic and blood CD4+ T cells did not differ significantly in the different experimental groups irrespective of viral dose, except for a significant splenic CD4+ T cell accumulation after 105 RIU 3CKO infection and significant HLA-DR up-regulation on spleen and blood CD4+ T cells after wt infection and a trend in HLA-DR up-regulation for 3AKO and 3CKO infection (Fig 2B and S2B, S3E, S3F, S3G and S3H Figs).