Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of IRG1high versus IRG1low macrophages identified the TNF signaling pathway as the most enriched pathway in IRG1high cells (Fig. S1g), suggesting a potential link between TNF-α regulation, IRG1 expression, and ITA production in the context of RA. The gene discussed is TNF; the disease is rheumatoid arthritis.