In addition to immune cells, IVD cells themselves are able to produce IL-1β. A low expression of IL-1β is observed in non-degenerate human IVDs, revealing the involvement of IL-1β in normal disk tissue repair and remodeling [38]. However, degenerate and herniated IVDs display higher IL-1β levels than non-degenerate IVDs [38]. Moreover, IL-1β levels in degenerative human IVD tissues increase with severity of degeneration [39]. In AF and NP biopsies intraoperatively collected from ten lumbar disk