In some cases, the nucleus macrophages attack the nucleus pulposus, and start secreting inflammatory cytokines, like tumor necrosis factor alpha, an interleukin-1, and interleukin-6.
Between each of the vertebral bodies is an intervertebral disc which is made of type I and type II collagen and has two parts, the annulus fibrosis, an outer fibrous ring, and the nucleus pulposus, an inner jelly-like substance.