Since almost all patients with CLL have a high prevalence of EBV (94%) [31] and thus possess EBV-specific memory cells with a high frequency of CD4+ gp350-specific T cells [32], the incorporation of gp350 into exosomes has a dual function: it confers B-cell tropism and serves as an immunodominant viral CD4 antigen. Here, CD4 is linked to B-cell chronic lymphocytic leukemia.