CLEC2D and acute lymphoblastic leukemia: Moreover, on NK cells we observed an increased expression of LLT1 in the very high-risk, high-risk, and standard risk/low-risk ALL patients both before and after chemotherapy treatment as compared to the healthy individuals (Figure 3E-F), which may potentially cause chronic activation of NK cells and be an indicator for NK cell exhaustion, which is where they are unable to recognize malignant cells and carry out the cytotoxic effects [33,64,65].