CD19 and B-cell chronic lymphocytic leukemia: The percentage of CD86, a costimulatory marker, was significantly increased in the SID EBV + and CLL EBV + groups, both on CD4+ (Fig. 5J) and CD8+ (Fig. 5K) T cells, as well as on CD19 + B (Fig. 5L) cells, which may indicate an enhanced activation of immune cells in response to EBV.