Intestinal IFNα4 drives the progression of PAH by inducing the expression of IFI44 in CD8+ T cells and promoting TRAIL-mediated endothelial cell apoptosis, revealing the key role of metabolic signals in the gut-immune axis (Li et al., 2024d; Ruffenach et al., 2024). Here, CD8A is linked to pulmonary arterial hypertension.