Importantly, granzyme B and perforin constitute the main components of the cytotoxic cargo of cytotoxic lymphocytes (cytotoxic T lymphocytes and NK cells) and thereby mediate target cell death [20]; thus, the upregulation of granzyme B and perforin in the bone marrow NKG2D+ MAIT cells after their exposure to the NKG2D-Ls is consistent with the reported ability of these cells to recognize viral infections [21]. Here, KLRK1 is linked to viral infectious disease.