PPIB and arthritic joint disease: To investigate whether and how macrophage training by β‐glucan exposure affects the susceptibility of arthritis synovial FLS to ferroptosis, rat β‐glu‐Mφ were co‐cultured with rat CIA‐FLS for 72 h in vitro, and then rat CIA‐FLS were stimulated with ferroptosis inducers (Figure4A).