Priming of both CD4+ and CD8+ T cells requires type I IFN signaling (10, 72, 73), and CD4+ and CD8+ T cell recruitment was shown to be impaired in type I IFN receptor α1 chain-deficient (CD118−/−) mice infected with HSV-1, pointing to a major role for type I IFN in the modulation of T cell priming during viral infection (74). This evidence concerns the gene CD4 and viral infectious disease.