CD4 and inflammatory bowel disease: i-OCLs arise under the control of persistent high levels of Rank-L, IL-17, and TNFα mainly produced by CD4+ T cells that play a major role in pathological osteoclastogenesis observed in osteoporosis and IBD (Cenci et al., 2000; Ciucci et al., 2015; Ibáñez et al., 2016; Li et al., 2011).