TNF and Arthritis: Given the limited number of iron-laden macrophages in Early arthritis in TNF-Tg mice, we conclude that inflammation alone is insufficient for the accumulation of iron in macrophages, and hypothesize that additional inciting events (e.g., phagocytosis of dead and dying cells and ferroptosis) are necessary to promote their generation and aggregation, which may be relevant to the clinical pathogenesis of RA.