Patients with FHF were found to have higher anti-HEV IgM and IgG titers than those with self-limiting infections [80], and PBMCs from patients with FHF were found to produce higher IFN-γ, TNF-α, IL-2, and IL-10 concentrations after stimulation with ORF2 peptides than PBMCs from controls. Here, TNF is linked to TNF receptor 1-associated periodic fever syndrome.