IL6 and Rett syndrome: The same authors found that the upregulation of NF-kB caused by MeCP2 deficiency enhances the expression of tumor necrosis factor alpha (TNFa), interleukin 6 (IL-6) and interleukin 3 (IL-3) (55), which can contribute to the subclinical immune dysregulation observed in RTT patients (56), including increased levels of TNFa and IL-6 in the blood, among other cytokines (57).