CD8A and psoriasis: For instance, Faecalibacterium prausnitzii helps protect against psoriasis by competitively inhibiting the colonization of pathogenic skin flora and producing SCFAs, which modulate inflammatory responses (25), and Lactobacillus casei helps reduce skin inflammation by decreasing the number of cytotoxic CD8+ T cells, thereby modulating the immune response and promoting skin health (26).