The analysis also shows that in the case of patients with CLL EBV+ in relation to CLL EBV−, a highly specific marker may be: the percentage of CD4+ PD-1+ and CD8+ PD-1+; percentage of total lymphocytes positive for PD-L1 (Figure 11A) and CTLA-4 (Figure 12A); the percentage of CD4+ CD86+ and CD19+ CD86+ (Figure 12A); and the percentage of total lymphocytes positive for CD200R and CD200 expression (Figure 13A). The gene discussed is CD274; the disease is B-cell chronic lymphocytic leukemia.