While B cells are typically linked to bone loss via osteoclast induction in conditions like rheumatoid arthritis and postmenopausal osteoporosis [94, 95], eosinophils secrete cytokines such as transforming growth factor beta (TGF-β) and leukemia inhibitory factor (LIF), which may promote osteoblast differentiation from mesenchymal or osteoprogenitor cells [93, 96–99]. Here, LIF is linked to rheumatoid arthritis.