TNF and rheumatoid arthritis: As we have already observed that macrophages are very radioresistant [31, 39] and LD-RT reduced the inflammatory phenotype of FLS in an experimental mouse model of RA (human TNF-α tg mice, strand tg197; hTNF-α tg) [28], we now aimed to investigate for the first time the effects of LD-RT in a conditioned medium system of FLS and bone marrow-derived macrophages in an experimental model of RA on macrophage phenotype.