Apparently, selective immunodeficiencies affecting B-cell function (e.g., CD40, CD19, CD81 deficiencies) or antigen-dependent CD4 T-cell activation (i.e., HLA-II deficiency) do not predispose to severe EBV infection, suggesting that these immune functions are not essential for EBV control [38]. Here, CD4 is linked to Epstein-Barr virus infection.