IFNG and Menkes disease: On the basis of these experimental studies, an up-regulated expression of IFN-γ in the luminal fluid of ES from patients with MD compared with those of controls, and a positive expression of IFN-γ in the epithelial cells lining the sac, could be expected to decrease Na+ transport in the ES lumen, which may consequently cause higher luminal [Na+] and an increased luminal fluid volume, since water shift usually accompanies Na+ movement.