CTLA4 and B-cell chronic lymphocytic leukemia: In the EBV- CLL group, particularly strong negative correlations were observed for miR-15a-5p and CD4 + CTLA-4+ (R = −0.757, p = 0.001) and miR-142-5p and CD8 + CTLA-4+ (R = −0.671, p = 0.006), suggesting that reduced levels of these miRNAs are associated with higher activity of the CTLA-4 pathway, which plays a key role in the induction of immunosuppression and functional exhaustion of T lymphocytes.