Furthermore, based on the results of immune infiltration analysis, a significant positive correlation between ISG15 and IFI27 expression and monocytes has been observed in both HIV-1 and PAH, and it could therefore be inferred that the upregulation of ISG15 and IFI27 promotes monocyte activation and differentiation into pDCs during migration by IFN stimulation56. Here, ISG15 is linked to pulmonary arterial hypertension.