CD9 and metabolic dysfunction-associated steatohepatitis: Fibrosis in MASH is linked to a profibrogenic macrophage population expressing the “Fab5” gene signature: TREM2, CD9, FABP5, osteopontin (SPP1), and GPNMB.12 To investigate whether CD4+ T cells influence this macrophage phenotype, we performed gene expression analysis on flow-sorted hepatic monocyte-derived macrophages (CD45+ Ly6G− CD11b+ F4/80+) from FFC-fed CD4−/− mice and WT controls (Fig. S1K).