It is known that NK cell effector function (cytotoxic activity) regulated by MAPK signaling cascades, including via the c-Jun N-terminal kinase (JNK) [76] signaling pathway, is dysregulated within patients with ME/CFS, who exhibit reduced NK cell cytotoxic activity [77]. The gene discussed is MAPK8; the disease is myalgic encephalomeyelitis/chronic fatigue syndrome.