Similar results were observed in levels of pro and active IL-1β protein as well as mature IL-1β and TNF-α mRNA in macrophages with transiently silenced GCN2 (Fig 2H, S5A, S5B and S5C Fig).The observed effects of HF were specific to GCN2 because PKR-specific small interfering RNA (siRNA)-mediated knockdown of PKR—another eIF2 kinase—did not affect HF’s ability to reduce IL-1β production, indicating a PKR-independent effect (S6 Fig). Here, EIF2AK4 is linked to hydrops fetalis.