IL17A and psoriasis: IL-23 and TNF-α mRNA expression levels were increased in exosomes from psoriasis patients (Sawamura et al., 2023), and IL-17A levels were significantly upregulated in exosomes from moderately severe patients compared to mild patients (Cordonnier et al., 2019), suggesting that exosomes can activate the IL-23/IL-17A-Th17 axis in receptor cells by delivering inflammatory mediators.