An earlier study on OPN neutralization in collagen-induced arthritis found that 23C3 reduced pro-inflammatory cytokines (many of which induce osteoclast differentiation and function) and promoted the apoptosis of type-II collagen activated T cells, thereby indicating a mechanism by which OPN neutralization by 23C3 improves arthritis and osteoporosis [208]. The gene discussed is SPP1; the disease is arthritic joint disease.